Update submodules: plugins (new commits)

plugins:
    a78b6fe Chris Smith <chris@dmdirc.com>
            Various style fixes.

            Gerrit: http://gerrit.dmdirc.com/3098

Change-Id: I6e2a7437e31a96fd9fcf22d75825ca83000e1d90
Update style rules.

Remove unused packages from NB import rules.

Set checkstyle line length to 100, add com.google import ordering.

Change-Id: I1e82e3f02e4e367bf56a5642560dbc8e25d73646
Reviewed-on: http://gerrit.dmdirc.com/3099
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager