-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/llhudeffectlookat.cpp

@@ -504,7 +504,7 @@ void LLHUDEffectLookAt::setSourceObject(LLViewerObject* objectp)
 //-----------------------------------------------------------------------------
 void LLHUDEffectLookAt::render()
 {
-	static LLCachedControl<bool> private_look_at("PrivateLookAt",false);
+	static const LLCachedControl<bool> private_look_at("PrivateLookAt",false);
     if (private_look_at &&
         (gAgent.getAvatarObject() == ((LLVOAvatar*)(LLViewerObject*)mSourceObject))) return;
 	if (sDebugLookAt && mSourceObject.notNull())