Setup revision control to drupal

[tmitchell]

• turn on revision control
• set it up as a default option
• install and test diff module for viewing changes

[tmitchell]

• Revision tracking and rollback is built into Drupal's core!
• Revision tracking is now enabled as a default for "page" content types. This is set in the administration menu -> settings -> content types -> page. There is a checkbox there to set the default. Now every page that goes through an edit->save process will show a 'revisions' tab next to 'edit' at top of a page
• Diff viewing is now enabled and appears in the revisions tab for any page that has revisions saved.
  • At present viewing of revisions and diffs appears to limited to authenticated users (i.e. not anonymous), but hopefully this is good enough for now.