[CTF] Bot related commands

The max possible number in the !changebots is now 3. (Mar. 9)

As you might already know, in CTF, you can now change the number of bots by using commands.

!changebots <number> – Specify how many bots you want to have on each team (0 – 3).

!kickbots – Remove all bots from both teams.

Do not worry as the server will not be empty.
If almost all the players have left the server, 3 bots will be put on each team automatically.