Changelog update

Forgot to do this when i added the servicebot stuff.
Merge pull request #2173 from GauHelldragon/master

Changelog!
Hydroponics trays will update icons after being weeded now.
Merge pull request #2174 from GauHelldragon/master

Hydroponics fix
required_players_secret added, which is the number of players needed for a game mode to start when that mode has been chosen at random.

required_players for most modes reduced to the number of antagonists + 1, as the variable is only used when the game mode is explicitly voted for.