[151] Notes Field 

Injected Notes Field into Page-like objects.

In order to see this working and validate language independence, should you feel so inclined:

Build a Simplified Chinese Site:

`python manage.py build_language_sites zh-cn`

~~Overwrite **LANGUAGES** in `projects.settings.local`:~~ no longer needed; added into base settings.

1. Update a Page's notes field in English
1. Utilize the language flipper
1. Validate the analogous Page has its own independent Notes value

The above is merely a sanity check, as each Page is its own instance, but for the sake of completeness (and sanity), I figured an outline of QA steps is reasonable.  Please advise if there are other requirements for this component.