Make sure plugins are compiled for Java 1.7.
Make sure plugins are compiled for Java 1.7.

Change-Id: Ibe571916d24aa437c38b94c037f61fb8d342b444
Reviewed-on: http://gerrit.dmdirc.com/3444
Reviewed-by: Greg Holmes <79e2475f81a6317276bf7cbb3958b20d289b78df@dmdirc.com>
Automatic-Compile: DMDirc Build Manager

csmith/DMDirc-Plugins,DMDirc/Plugins,DMDirc/Plugins,csmith/DMDirc-Plugins,csmith/DMDirc-Plugins,csmith/DMDirc-Plugins,DMDirc/Plugins,DMDirc/Plugins,DMDirc/Plugins,csmith/DMDirc-Plugins