MAINT-7383 Revise notification for Empty Trash / Purge trash action to include number of items being deleted.

MAINT-6805 Fixed Right-click menus in the right and left panes of the Conversations windows are different

A shocking number of LLSingleton subclasses had public constructors -- and in
several instances, were being explicitly instantiated independently of the
LLSingleton machinery. This breaks the new LLSingleton dependency-tracking
machinery. It seems only fair that if you say you want an LLSingleton, there
should only be ONE INSTANCE!

Introduce LLSINGLETON() and LLSINGLETON_EMPTY_CTOR() macros. These handle the
friend class LLSingleton<whatevah>;
and explicitly declare a private nullary constructor.

To try to enforce the LLSINGLETON() convention, introduce a new pure virtual
LLSingleton method you_must_use_LLSINGLETON_macro() which is, as you might
suspect, defined by the macro. If you declare an LLSingleton subclass without
using LLSINGLETON() or LLSINGLETON_EMPTY_CTOR() in the class body, you can't
instantiate the subclass for lack of a you_must_use_LLSINGLETON_macro()
implementation -- which will hopefully remind the coder.

Trawl through ALL LLSingleton subclass definitions, sprinkling in
LLSINGLETON() or LLSINGLETON_EMPTY_CTOR() as appropriate. Remove all explicit
constructor declarations, public or private, along with relevant 'friend class
LLSingleton<myself>' declarations. Where destructors are declared, move them
into private section as well. Where the constructor was inline but nontrivial,
move out of class body.

Fix several LLSingleton abuses revealed by making ctors/dtors private:

LLGlobalEconomy was both an LLSingleton and the base class for
LLRegionEconomy, a non-LLSingleton. (Therefore every LLRegionEconomy instance
contained another instance of the LLGlobalEconomy "singleton.") Extract
LLBaseEconomy; LLGlobalEconomy is now a trivial subclass of that.
LLRegionEconomy, as you might suspect, now derives from LLBaseEconomy.

LLToolGrab, an LLSingleton, was also explicitly instantiated by
LLToolCompGun's constructor. Extract LLToolGrabBase, explicitly instantiated,
with trivial subclass LLToolGrab, the LLSingleton instance.

(WARNING: LLToolGrabBase methods have an unnerving tendency to go after
LLToolGrab::getInstance(). I DO NOT KNOW what should be the relationship
between the instance in LLToolCompGun and the LLToolGrab singleton instance.)

LLGridManager declared a variant constructor accepting (const std::string&),
with the comment:
// initialize with an explicity grid file for testing.
As there is no evidence of this being called from anywhere, delete it.

LLChicletBar's constructor accepted an optional (const LLSD&). As the LLSD
parameter wasn't used, and as there is no evidence of it being passed from
anywhere, delete the parameter.

LLViewerWindow::shutdownViews() was checking LLNavigationBar::
instanceExists(), then deleting its getInstance() pointer -- leaving a
dangling LLSingleton instance pointer, a land mine if any subsequent code
should attempt to reference it. Use deleteSingleton() instead.

~LLAppViewer() was calling LLViewerEventRecorder::instance() and then
explicitly calling ~LLViewerEventRecorder() on that instance -- leaving the
LLSingleton instance pointer pointing to an allocated-but-destroyed instance.
Use deleteSingleton() instead.

MAINT-5362 Adding/detaching/taking off etc from the inventory view in appearance panel will add/remove the wrong item if a different item is selected in inventory floater

MAINT-4974 FIXED Complete name should be used in LLAvatarActions::buildResidentsString only when building name string for share confirmation dialogs

replace llinfos, lldebugs, etc with new LL_INFOS(), LL_DEBUGS(), etc.

consolidated most indra-specific constants in llcommon under indra_constants.h
fixed issues with operations on mixed unit types (implicit and explicit)
made LL_INFOS() style macros variadic in order to subsume other logging methods
such as ll_infos
added optional tag output to error recorders

STORM-1838 Added teleport request to conversation log.  Added xml to have message appear in IM window, if open.  Code cleanup.

CHUI-809 FIXED Changes in menu items to make them consistent. Do not start IM if selected person is self.

CHUI-633 FIXED User is not able to open chat history by 'View chat history' menu item from pop-up menu of People floater

CHUI-647 FIX "Conversations" floater is not opened when user wants to share something via "Conversation log" floater
Added call to show conversations floater in LLAvatarActions::share

STORM-1838 Break out a large block of code from handle_lure_callback so it can be called directly by teleport_request_callback.

CHUI-580 : WIP : Change the display name cache system, deprecating the old protocol and using the cap (People API) whenever available. Still has occurence of Resident as last name to clean up.

CHUI-337 FIXED: To avoid confusion with a classes "...conversation..." and in accordance with the naming convention in the project, some classes and corresponding files should be renamed:
LLIMConversation -> LLFloaterIMSessionTab
LLIMFloater -> LLFloaterIMSession
LLNearbyChat -> LLFloaterIMNearbyChat
LLIMFloaterContainer -> LLFloaterIMContainer
LLNearbyChatBarListener -> LLFloaterIMNearbyChatListener
LLNearbyChatHandler -> LLFloaterIMNearbyChatHandler

CHUI-484: Updating the code to rather than refer to it as Busy Mode, it now refers to it as Do Not Disturb mode.

CHUI-383: Realized that prior changes for this bug caused a regress. The regress was using the people panel or a notecard to start a im/call with a user. When doing this the conversation line item would not be focused. Resolution: Changed all calls to LLIMFloater::show() to LLIMFloaterContainer::showConversation(), which will first select the conversation line item and then show the corresponding conversation floater.

CHUI-422 : Update the ad-hoc conversation with the known list of on line agents without waiting for server message (which often doesn't come...).