-LLCached[COA]Control can now be static const. Use for readonly access.

-const'd all readonly LLCached[COA]Controls to prevent altering by mistake.
-added get() accessor to LLCached[COA]Controls to return cached type explicitly without manual casts.
-added missing operators to LLCachedCOAControl
-Converted a few more settings to LLCached[COA]Control
-Fixed LLColor4U -> LLSD -> LLColor4 problems in LLCachedControl

Ascent functionality fixes:
-Tag coloring pulled out of getClientInfo(Redundant. idleUpdateNameTag already handled it)
--Tag and color substituted at render-time. Simple boolean logic. Neglible perf penalty.
-Fixed llinfos spam if AscentShowSelfTagColor = false
-Client tag updated less superfluously

indra/newview/llviewermessage.cpp

@@ -2784,7 +2784,7 @@ void process_chat_from_simulator(LLMessageSystem *msg, void **user_data)
 
 			if (!is_muted && !is_busy)
 			{
-				static LLCachedControl<bool> use_chat_bubbles("UseChatBubbles",false);
+				static const LLCachedControl<bool> use_chat_bubbles("UseChatBubbles",false);
 				visible_in_chat_bubble = use_chat_bubbles;
 				((LLVOAvatar*)chatter)->addChat(chat);
 			}