Serialise project refresh for multi-module projects.
1. Add lein projects based on content roots, not module name.
2. Check that modules are not managed by Maven when adding, and try to tidy up ex-maven modules.
3. Don't magically import project files on file add.
4. Allow projects to be added from the context menu.
5. Allow projects to be removed from the toolwindow.
6. More readable library names.
7. General code tidying.
Fixes cursiveclojure/cursive#27.
Merge branch 'master' of https://github.com/cursiveclojure/intellij-leiningen-plugin