Add ability to add / del / process botcmds

- Added add_botcmd function which registers a function as a bot command
- Added del_botcmd function which unregisters a function as a bot command
- Added _process_botcmd which determines if a msg is a botcmd and calls the
   botcmd function for processing.
GH-5 Fixed issue with plugin responding to every msg
Initial work on admin plugin