Add a method to return a display string for the location. The format of the string varies depending on what data is available for the location.

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Use the -[VenueLocation locationDisplayString].

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Add a function to convert a CLLocationCoordinate2D to a Degree-Minute-Second string

Signed-off-by: Blake Skinner <bskinner@mit.edu>