Feature/use current location

Optionally show directions from current location.

Before transitioning to directions view, prompt user what origin to use (either entered address or current location), then show directions for selected origin.

In case current location selected but location services disabled, will prompt to enable location services, then re-query once location found.

Also changes redundant search button on home view to contact selector button.
I believe we discussed this in the PR for formatting addresses from the API; no, you'd have to override toString() anyways (the in-built one returns weirdly-formatted junk).  Also, depending on the context, it might be desirable to have newlines, or a single-line address, or add or remove other stuff.