[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/migrations/9.0.2.0.0/post-migration.py

@@ -0,0 +1,12 @@
+# -*- 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 categories template to its content
+    cr.execute("""
+        UPDATE document_page
+        SET template = content
+        WHERE type = 'category'
+    """)