Proper search support for binary Groovy files

We need to support Java search of the contents of binary groovy files

As described in GRECLIPSE-856, the first step is to create a GroovyClassFile class.

Then, we need to ensure that LanguageSupport.maybePerformDelegatedSearch() also works on GroovyClassFiles.

Finally, we need to ensure that this method is also called on GroovyClassFiles (currently, binary files are ignored).