Workbench Translation

This is a first try of integrating some language/translation related workflow with the Workbench suite.

For feedback on this module, please see #1379080: Workbench Translation module ?

For now it adds some translation related status to Workbench Moderation and provides some views on the Workbench page to quickly track and access your translations.

The idea though is to provide some more automation later like:
- Publishing the whole translation set when the source content is published (partially implemented)
- To hold off publishing of still not translated content (TO DO)
- Keep track of from which revision of the source content a translation is done (partially implemented).

The workflow for the source content would be like:
1. Draft
2. Needs review
3. Needs translation (waiting for all translations to be ready)
4. Published

The workflow for a translation:
1. Draft
2. Needs review
3. Translation done
4. Published (it may be done automatically when the translation source is published)