Added setSwipeable methods for Card and CardStack objects.
When determining if a card is swipeable, Card is first checked and given the highest priority. If the cards swipeable hasn't been set, we check CardStack next, followed by the StackAdapter.

Signed-off-by: Brian Muse <brian@onemightyroar.com>
Updated the Example activity to demonstrate swipeable micromanagement.
Updating project properties to SDK level 17 for Example app.