Add Forms table columns for storing and evaluating predicates.
Read predicates from new forms and store them in the forms database.
Display only surveys needing a response in SurveysActivity.
Add simple predicate solver. Currently just checks to see if forms have been answered within a given number of milliseconds.
Evaluate all predicates when the NotificationService starts, and only generate a notification if some passive survey needs a response.
Update the lastResponse and needsResponse form columns when completing an instance.
Merge pull request #29 from rjbailey/predicates

Add support for displaying forms conditionally.