Circle CI improvements.

Build meta, not just plugins.
Expose plugins as artifacts.

Fixes DMDirc/Infrastructure#62
Add silly hacks to make Gradle behave.

Add fake jar/test tasks with dependencies on the subprojects.
Make dependencies depend on subprojects.
Pull from the right project...
Right artifacts path
Merge pull request #85 from csmith/master

Annoying Circle CI changes.
Merge branch 'master' of https://github.com/DMDirc/Plugins into java8