[Core] Chat commands disabled for normal players.

A new setting for the world server has been added. From now on
chat commands executed by normal player accounts will no longer
be executed, unless you explicitly enable the `PlayerCommands`
option.

By default player command execution is disabled.

Signed-off-by: Daniel S. Reichenbach <daniel@kogitoapp.com>

Conflicts:
	ChangeLog.md
	src/game/Chat.cpp