Adds "All Data" filter to case list report

Addresses this ticket:
http://manage.dimagi.com/default.asp?121778#688842
It adds an "All Data" filter by modifying the `CaseListMixin` class that is subclassed by `CaseListReport`. I've examined the code of `CaseListReport`'s descendants, and none of them seem to cause conflicts with the changes made.
Even more clear might be:
```
url(r'^emwf_options/)$', api.EmwfOptionsView.as_view(), name='emwf_options'),
url(r'^emwf_options/all-data/)$', api.EmwfOptionsView.as_view(), {'all_data'=True}, name='emwf_options_with_all_data'),
```