fixes #25 - uses the extension point “org.eclipse.xtext.ui.shared.sharedStateContributingModule” (introduced in Xtext 2.5.0) to replace Xtexts own JdtClasspathUriResolver with Sculptors MavenClasspathUriResolver in Xtexts internally used XtextResourceSet to support Maven resource folders excluded by the M2E Eclipse plugin
updates documentation and removes commented stuff + unused XBase Java type support