Add custom empty table cells for Candidate Details
Add template class for empty handling of single-section table views

To use:
  - Set self.tableView.dataSource to an instance of this class
    if the table view has no data to display.
  - Inspired by:
    http://blog.yangmeyer.de/blog/2013/05/11/best-practice-handling-empty-table-views
Add VIPEmptyCell model + xib
Implement VIPEmptyTableViewDataSource with custom cell xib
Implement VIPEmptyTableViewDataSource for Ballot/Details views
Implement VIPEmptyTableViewDataSource for FindElections View
Implement VIPEmptyTableViewDataSource for PollingLocations table view
Add empty table cells for Contest Details view
Merge branch 'develop' into feature/empty-table-errors
Update PR with feedback

  - Add NSLocalizedString comments
  - Refactor setEmptyMessage
Merge branch 'feature/empty-table-errors' into develop