Add spectate messages

May be disallowed or frowned upon so it should be announced.
Remove panel updates when someone readies up

The panel is on a 1s timer already so this is not needed and just lets
people have a ghetto DoS.
Added new caster management system

`sm_resetcasters` must now be run in confogl_off.cfg to reset the caster
trie.  Two new functions have been added to readyup.inc to allow other
plugins to check if a given client or Steam ID is a registered caster or
not.
Merge branch 'master' of github.com:CanadaRox/l4d2readyup