Added COMMANDO_PLUGINS and TFTP_HOST to settings
Adjustments to allow for sending kwargs to xmlrpc methods.
Added 'force' option to add_handler method
Various plugin tweaks.

- Moved xmlrpc_config_device() into config_device module.
- Removed 'self' from args in xmlrpc_* methods.
- Changed config_device logging to use twisted.python.log
Removed xmlrpc_config_device() from xmlrpc/server.py.