Move more logic to the helper modules

- Diff view changes
-- Only show pool description changes in diff view
-- Conditionally render diff link when applicable values are changed
-- Conditionally show diff view sections when values are changed
- Show renames on index view
-- There is plenty of space
-- This wasn't shown at all for wikis
-- Having to navigate to an alternate page is unwieldy for pools
- Show "posts" as a status on pools
-- This is so all changes among versions are quantified as a status
- Standardize diff/index titles

app/views/note_versions/index.html.erb

@@ -1,6 +1,6 @@
 <div id="c-note-versions">
   <div id="a-index">
-    <h1>Note Changes</h1>
+    <h1>Note History</h1>
 
     <%= render "listing" %>