Enable source attachments on libraries in the 'Bnd Bundle Classpath'

The current implementation stores source attachment data (if there is any) for each library exposed via the BndClasspathContainer. The attachment paths are persisted to a properties file per project.

There is also partial support for eclipse style source bundles, that is bundles that are of the form <bsn>.source are attached to bundles as source if there is not already a source attachment set.
Remove files not in scope for project
This will avoid unnecessary building. This is maybe not the optimal
solution, but has less overhead than building projects that do not need
to be rebuilt.
Handle files included by the -include directive in build.bnd
Add null check on IResource.getLocation()
Merge pull request #486 from ateirney/bndclasspathpersister

Enable source attachments on libraries in 'Bnd Bundle Classpath'