[Feature] Finish FavoriteRoute

[pingzing]

This is a candidate for being pushed back to 1.2.

• Allow a favorite route to pinned to the Start Screen
• Allow a favorite route to be pinned to the Main Page
• Make tapping a favorite route on the Favorites page instantly try to plan a trip with that route.
• Make its appearance on the Favorites page a little less ugly, and also less misleading: make it a transparent, dashed line from point A to point B.
• Expose it on the SearchPage as a CommandBar button. Make the button open a flyout asking the user to select the route to save. Upon saving, show a 'saved!' message (how?)

[pingzing]

This is finished-ish. I'd like to come back to this later because the following problem still exists:

• When we save a Favorite Route, we save the entire route so we can display it back on the Favorites Page's map later. However, this is misleading--we really only use the start and endpoints. Need to come up with a better way to show that, visually. Maybe just a straight, as-the-crow-flies dashed line?

Either way, pushing that to 1.1.