KML I/O added in Developer Menu

This adds KML import and export. 

[In debug-only, if you long-press the version number in the about dialog, you get the KML I/O dialog.] EDIT: no longer true.

I have been using this feature to export data for verification, and to load test 1000s of points into the map view for load testing. The feature is not ready for prime-time, as the UI needs more work, but other than that it is functional.

I don't want to keep merging this locally for testing, so it is best to get it in the codebase.

@crankycoder r?