Update submodules: plugins (new commits)

plugins:
    bee928c Greg Holmes <greg@dmdirc.com>
            Move window management into seperate class.

            This also changes the behaviour of the look and feel and
            textpane font and size preferences and they now require a
            restart.

            Gerrit: http://gerrit.dmdirc.com/3308

Change-Id: I8fe99fb98f88a6bf34a8e87464423b30bd97262d