Adds typing indicator.
It's toggleable as client preference.
Displays dots(codersprite) near the mob when he starts typing a message.
Detects chatline me and say via checking contents.
Detects shortcut input me an say via hacky wrapper that's called now instead of direct say/me verbs.
Added tracking of inactivity in chatbar.
Now indicator will disappear if for 30 seconds contents of chatbar didn't change.

Moved all relevant vars to the typing_indicator.dm
Added 'typing' var, as 'if(!(typing_indicator in overlays))' didn't work and overlays kept being added forever.
Fixed preference toggle feedback being backwards.
Fixed wrong verb called in hotkeys mode.
Merge pull request #6212 from comma/typing

Adds typing indicator.