[IMP][9.0] Change Requests and workflow improvements on documents (#155)

* [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

document_page_approval/migrations/9.0.2.0.0/post-migration.py

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 Ivan Todorovich <ivan.todorovich@gmail.com>
+# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl.html).
+
+
+def migrate(cr, version):  # pragma: no cover
+    # Set all pre-existing pages history to approved
+    cr.execute("""
+        UPDATE document_page_history
+        SET state='approved',
+            approved_uid=create_uid,
+            approved_date=create_date
+        WHERE state IS NULL
+    """)