Utility waypoint un/boxing
Refactoring to allow push of (mission item) detail view on table view

- WaypointsViewController is no longer a TableView source/delegate
- now holds a container view, which embeds a UINavigationController
with a root controller of MissionItemTableViewController (a newly
introduced controller class)
- all tableView source/delegation has been moved from
WaypointsViewController to this new controller
- on edit row selection, MissionItemTableViewController pushes/performs
storyboard segues to instantiate the detailed view (for now,
essentially a static view with a UIPickerView for command type)