Update submodules: plugins (new commits)

plugins:
    c6ed9e1 Chris Smith <chris@dmdirc.com>
            Pass in CommandControllers to some plugin commands

            I got bored about half way through, so more to go at some point.

            Gerrit: http://gerrit.dmdirc.com/2807

Change-Id: Id751bc784de3d697deb3199f09143dba427651b1