Adds support for placeholder fields with dynamic slot generation.
Adds tests and fixes leak in field.
Merge remote-tracking branch 'upstream/develop' into dynamic-placeholder-field
Adds documentation.
Removes magical slotname generation in favor of explicit callables.
Removes unused import.
Moves validation for placeholder field to  init, also now explicitely checks for type string.
Document customizing menus. Partially fixes #936
Fix test dependencies:

* made django-reversion fixed to 1.6.6, otherwise it would download 1.7.1 which doesn't work with django 1.4
* added missing test requrements: djangocms-text-ckeditor, djangocms-column, djangocms-style
Fix whitespace issue
revert changes unrelated to page-extensions
use OneToOneField to allow optimising with select_related
auto set extended_object on add
page extensions: check permissions
fixes an issue with redirect on delete
remove console logs
decrease default timeout
Adds support for plugin actions.
Document the required messages framework
Merge pull request #2119 from yakky/feature/docs_messages

Document the required messages framework