Feature/map intents

Adds clickable map buttons for transportation directions. Map button clicks launch an implicit intent with the correct form of directions given (driving vs transit).

Hadiyah, after reviewing a few more Android apps on my phone I decided that the button on each line was the right idea, after all. :)

This branch piggybacks on the Waiting Screen work, because that is where the origin/destination work was most recently corrected, and that's out for comments.

Please do not merge this branch for me: I would like https://github.com/sachishah/airportstatus/pull/11 to be accepted first.