AO Refactor

Should fix AO not turning on without opening floater first

Cleans up code
Reduces memory footprint, especially when not in use
Removes unused functions and parameters
Decouples AO from Floater class (AOSystem)
Removes duplicate Idle state
Formalizes singleton patterns of globals
Centralizes override handling into override structs
Fall back on simple english notecard explanation when missing config ini
Fixes sitting override playing when sitting is disabled (and acting weird)
Moves the bulk of override handling into override structs
No longer state-based, now tracks using per-struct playing field

indra/newview/llagentcamera.cpp

@@ -2265,7 +2265,8 @@ void LLAgentCamera::changeCameraToMouselook(BOOL animate)
 		mMouselookTimer.reset();
 
 		gFocusMgr.setKeyboardFocus(NULL);
-		if (gSavedSettings.getBOOL("AONoStandsInMouselook"))	LLFloaterAO::stopMotion(LLFloaterAO::getCurrentStandId(), true);
+		auto ao = AOSystem::getIfExists();
+		if (ao && gSavedSettings.getBOOL("AONoStandsInMouselook")) ao->stopCurrentStand();
 		
 		updateLastCamera();
 		mCameraMode = CAMERA_MODE_MOUSELOOK;