History page in new templates

Pages that need to be ported:
- [x] revisions table
- [x] compare revisions page
- [x] dataset revision page
- [x] revision list page
- [x] group revision page

Branch: https://github.com/okfn/ckan/tree/368-new-history-page

The group revision page still shows an error. `UndefinedError: 'dict object' has no attribute 'num_followers'`