Add map cooldown and min/max player configuration, saving of map cooldown state

[m-arcuri]

Adds a new values to maplist.cfg:

"cooldown"

• Use this to configure the cooldown length of each map individually

"minPlayers"

• Set the minimum players required to be online to nominate the map

"maxPlayers"

• Set the maximum player limit for nominating the map

Map cooldowns are counted at the end of next map vote instead of at the end of the current one, matching the old CS:GO map manager behaviour.

Using !nominate without any arguments and without having nominated a map will instead list all maps and their cooldowns in console. If a map cannot be nominated due to Min/Max player limits, it will display this information.

Writes cooldown keyvalues to "addons/cs2fixes/configs/cooldowns.cfg" whenever map cooldowns are decremented. This file will be read when the map list is loaded to restore the remaining cooldown lengths from the previous session. If not found, all maps will start as available to nominate.

[Vauff]

Also need to remove existing nominations if player count goes out of bounds, and notify those nomination owners.