CHUI-668: Now when exiting DND mode, the user's most intrusive notification will be used to notify that user (if received IM's during DND mode). Nearby chat messages/settings are ignored.

CHUI-668: Not fully complete but as of this commit, have functionality to use the user's most intrusive chat notification upon exiting from DND mode with IM's. Also if in DND mode, clicking on a conversation line item or floater, will flush the DND notifications system of storing that conversation. This way upon existing DND mode already responded conversations won't be notified to the user.

CHUI-580 : Fixed : Avoid fetching names while reacting to display name checkbox change (overkill), make display name pref disabled when usePeopleAPI is off

Reviewed by VoidPointer

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.

Path-643. Once the preferences panel is closed (either through ok or cancel), the pathing console rebuilds the gfx data.

EXP-1942,EXP-1945: Altering behavior when setting maturity preference to check the server response in an effort to ensure the viewer and server remain in sync.  This is a partial commit as I still need to add user behavior and notifications when things go wrong.

EXP-1849 FIXED Privacy settings could be set to default when modifying other preferences before login.

Ported with owner permission from Firestorm, inital work done by LordGregGreg Back

* Floater updates for positioning and to revert some earlier string changes.

SH-2276 Fix for failed assertions reported from debug-enabled viewers.  Also, remove "Basic Shaders" as a user settable option (shaders are always on if GL version >= 2.0, always off otherwise)

- Removed all sidetray dependencies and the sidetray itself.

- Also removed LLFloaterSidetrayTab and LLSidetrayListener as unused.

- Added a floater for People side tab.
- Replaced calls to LLSideTray with LLFloaterSidePanelContainer.

Changes:
* Click and double click in-world can now trigger click-to-walk or
  click-to-teleport actions, depending on preferences.
* Grouped keyboard- and mouse-related settings in Preferences -> Move.

LLProxy: Added another attempt to download gpu and feature tables after successfully setting up a proxy.

Other minor changes:
Clarified why we are using SOCKS5 as the "grid" argument to store proxy credentials.
Added class wide logging to the LLProxy class.