algorythmic improvement for MAINT-6891

CHUI-983 FIXED Call showHistory() after clicking toast as it was before. Minor change in showHistory()

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-315 (Nearby chat messages do not appear in conversation floater): cancelled inheritance LLNearbyChat from LLSingleton; set mSingleInstance flag for it.

Fixed warnings when creating a nearby chat toast.

removed special case logic for dealing with user online/offline collisions
added ability to cancel old duplicate notifications

EXP-1316 Minimized Snapshot floater has a snapshot preview image attached below.
EXP-1318 Clicking on nearby chat toasts should bring up Nearby Chat history

STORM-1021 ADDITIONAL_FIX Replaced usual object inspector with the remote one in nearby chat toasts.

STORM-578 FIXED using the color setting for "URLs" from Preferences for names in Nearby Chat toasts.

STORM-578 FIXED SLURL to object or user name in nearby chat toast now uses the font color selected in Preferences->Chat.
Removed unused "ChatToastAgentNameColor" setting from colors.xml.

STORM-390 FIXED "Place Profile" appeared instead of "Resident Profile" after clicking on user name in a nearby chat toast.

Now clicking an avatar name opens avatar profile; clicking an object name opens object inspector.

This change rolls back the fix of STORM-358.

streamlined LLUICtrlFactory's interface

removed redundant functionality
moved buildPanel to LLPanel

Reviwed by Igor Borovkov at https://codereview.productengine.com/secondlife/r/371/

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fix for EXT-6064 Clicking avatar name in nearby chat toast opens nearby chat history instead of avatar profile.
https://codereview.productengine.com/secondlife/r/287/
reviwed Vadim Savchuk

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Fixed normal bug EXT-4766 - System notifications in nearby chat has default avatar icon and behave like sent from object
Updated nearby toast to display system icon for system message.

Reviewed by Vadim Savchuk - https://codereview.productengine.com/secondlife/r/208/

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partitial fix for normal task EXT-2957 [BSI] Implement object icon for chat from objects, instead of using generic image for missing profile picture

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EXT-1847 Regression in the design spec: "You" should be replaced by your full avatar name in communication

also move real action from mouse_down to mouse_up (since clicking on url is processing in mouse_up).

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for information - since I think that messages from nowhere is bad practice for user - if object that send message has no name I use object id as name

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