In-line Analytics

PR for internal review purposes as prelude for PR to upstream
    PR'd against copy of upstream master.

Known issues to be fixed later:
- Styling is embedded in html file as prelude to re-styling
- No tests
- pep8 and pylint not looked at yet.

@jbau @jrbl @stvstnfrd @caesar2164 if you please.
Forgive me if you already planned to do this as part of your pep8 cleanup, but:

If you format docstrings with a summary line, newline, body format, then automagical documentation extraction doodads can do their dadding better.  Also pep8 suggests a more imperious tone.  So in general I prefer a layout like:
```
"""
Determine the problem type for the in-line analytics display.

Supported problem types are:
  - checkboxgroup
  - radiogroup

Other problem types return None.
If settings.ANALYTICS_DATA_URL is unset, return None.
"""
```
I really like the docstrings; I'd just like to see them tightened up as part of your cosmetics pass.