Fix the dependency-switheroo script.

Excluding 'com.dmdirc:util' nuked the project as well. That wasn't
good. Instead, just call remove on the DependencySet. That seems
to work and is a lot simpler.
Add clover support.

`./gradlew clean cloverAggregateReport` in meta will create a new
report for all the projects with tests.

Plugins that don't have any tests won't show up at all.