Added call to excmd_server_version inside init.sqf

The excmd_s DLL was not being loaded until the extension was called.
Meaning the named pipe was not initialised. This commit fixes that issue.
Infrastructure for command handling developed

Basic structure for command handling has been implemented. Commands are
listened for by handler functions which handle the implementation details
of each command. CBA_fnc_addEventHandler is used to implement a command
bus making expansion easier.