Provide a CachingUpdateManager.

Change-Id: Ia79f9199e8ca40dc3031234569a44da042fc617f
Reviewed-on: http://gerrit.dmdirc.com/3026
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Update submodules: plugins (new commits)

plugins:
    8916d98 Chris Smith <chris@dmdirc.com>
            Inject update manager in a few places.

            Again, add a deprecated method to SwingController/Manager to escape the dependency
            hell temporarily.

            Depends-On: Ia79f9199e8ca40dc3031234569a44da042fc617f
            Gerrit: http://gerrit.dmdirc.com/3025

Change-Id: I89bdcb6035f747be8fbe272a4b4f39bc3e8dbaac