CeylonModelLoader for #1316: remove duplicate declaration error from the backend
LanguageCompiler #1316: record every module tree by name
LanguageCompiler #1316: recover from module descriptor parse errors by making a pretend module
LanguageCompiler #1316: do not produce any class files for modules with errors
Test for #1316: moved it out of issues test into recovery test

And beefed it up to include errors in module descriptors