Exclude groovy and friends from the tests as well.

See #39.
Be sure to export the necessary files in the build

Right now this is not going to cause any issues but when we actually
export our plug-ins, we should be careful that we include all necessary
resources.

It is not a problem now because in this plug-in development environment,
everything is copied.
Create new separate plug-in project for ExtractClosure tests

This makes the separation cleaner since this test needs the JDT UI.
The previous one, i.e., edu.illinois.

See #39.