Fix bug in name hashing. Update test.
Rewrite ExtractAPITest to be JUnit test again.

This way I get much nicer Eclipse support.
Removed dead code from NameHashingTest
Always hash definitions in structural types.

Fixes source-dependencies/struct-usage scripted test.
Make use of newly defined utilities in NameHashingTest
Switch back to 0.13.1-SNAPSHOT as version number.

This makes it easier to test because sbt considers
0.13.1-SNAPSHOT and 0.13.0 to be binary compatible.
Add eclipse plugin configuration.