Handle javascript exceptions "gracefully"

The error message itself might need a bit of tweaking, but it's good to
at least have interesting information from the JS engine
- Added module test suite (run via MuteInterpreter)
- Added "has" and "get" utility methods for module scripts on value collections
Clean-up and remove Rhino dependencies

- Removed Rhino support code and libraries
- Merged Nashorn specific copies (build and jar) into original file
- Updated interpreter jar (not strictly speaking necessary)
- Fixed a typo in an error message
Merge commit '1a20e25ceb98376ff5c07456211b86233d78c377' into nashorn

Conflicts:
	src/ValueCollection.java
Fixed warnings