Fix UserElection properties can be null

Manifested as polling picker showed null for all
locations because filtering with the first array
being nil resulted in all locations option
for filterPollingLocations: resulted in nil response.

Added appropriate test
Replace UISegmentedControl with MMPicker for polling locations

With the addition of dropOffLocations, there is not enough space
to add the text for an additional item to the
UISegmentedControl
Add drop off locations to app polling view

Filters on isAvailable
Update localized strings for Dropoff feature
Update dropoff icons
Streamline PollingPicker button style
Merge branch 'feature/dropboxes' into develop