Cleanup

- Replaced 'EXP' with "Playtime' in most admin-visible locations. The
system is still invisible to normal players.
- Changed the types of exp you can accumulate from 'all', 'eng', 'sup',
etc to more human-friendly names like 'Crew', 'Engineering', and
'Supply'.
- Eliminated some copy-paste.
- Added a new configuration option: use_exp_restrictions_heads_hours.
When enabled and set to a >0 value, it overrides all head/ai job
playtime requirements, instead substituting that number of hours.

code/modules/admin/admin.dm

@@ -43,7 +43,7 @@ var/global/nologevent = 0
 	if(M.client)
 		body += " played by <b>[M.client]</b> "
 		body += "\[<A href='?_src_=holder;editrights=rank;ckey=[M.ckey]'>[M.client.holder ? M.client.holder.rank : "Player"]</A>\] "
-		body += "\[<A href='?_src_=holder;getexpwindow=\ref[M]'>" + M.client.get_exp_general() + "</a>\]"
+		body += "\[<A href='?_src_=holder;getplaytimewindow=\ref[M]'>" + M.client.get_exp_general() + "</a>\]"
 
 	if(istype(M, /mob/new_player))
 		body += " <B>Hasn't Entered Game</B> "