Update build for new plugins layout

Change-Id: I303b6b69518468f98d48d835b8f40135d9e4bcbf
Reviewed-on: http://gerrit.dmdirc.com/3849
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Update submodules: plugins (new commits)

plugins:
    93d4056 Chris Smith <chris@dmdirc.com>
            Gradle-ify the plugins.

            * Move all plugins to their own top-level directories.
            * Move resources out of source trees
            * Add Gradle build scripts.
            * Remove ivy and ant build scripts.

            Depends-On: I303b6b69518468f98d48d835b8f40135d9e4bcbf
            Gerrit: http://gerrit.dmdirc.com/3850

Change-Id: I1834fffb980aa5e790a858b2d376e9e445fabf2f