[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/views/report_document_page.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<openerp>
+<data>
+
+<template id="report_documentpage_doc">
+    <t t-call="report.external_layout">
+
+        <div class="page">
+            <h1 t-field="doc.display_name" />
+            <div t-raw="doc.display_content" />
+        </div>
+    </t>
+</template>
+
+<template id="report_documentpage">
+    <t t-call="report.html_container">
+        <t t-foreach="docs" t-as="doc">
+            <t t-call="document_page.report_documentpage_doc" />
+        </t>
+    </t>
+</template>
+
+
+<report 
+    id="report_document_page"
+    string="Document Page"
+    model="document.page" 
+    report_type="qweb-pdf"
+    file="document_page.report_documentpage" 
+    name="document_page.report_documentpage" 
+/>
+
+</data>
+</openerp>