edited docstring in admin.py

reworded the docstring for _do_moderequest in admin.py. Now makes clear
that it only handles ban and quiet modes, not any mode.
added chanserv bug workaround to ircop.py

Chanserv's QUIET and UNQUIET commands apparently don't support extbans.
Added a workaround to _do_connector_operation, which should be the main
entry point for all plugins requesting quiets or unquiets. If the target
starts with a $, submits it as a raw mode request instead of a connector
through chanserv.