* [document_page] FIX creating history when there are no changes made. Add history name field, to name revisions. Modified views to allow setting this field.
* [document_page] FIX BUG: UI hanging when editing content. This was due to the api.depends on _compute_diff. Removing it because it's not really necessary since the field is not stored.
* [document_page] page_id should be readonly.
* [document_page] Implement active field
* [document_page] Update version number
* [IMP] Refactor document_page_approval to always use states, and a few code improvements
* [IMP] Add QWeb report to print document pages
* Categories don't save content
* FIX Last Contributor (uid and date). Use related fields instead of computed where possible.
Fix search views, store some fields to make them searchable, added filters
* Add api.depends on computed diff
