Tapping within ~50px of the selection end handle on iOS doesn't trigger a click event. This commit ensures that our quote buttons are always at least 50px away from the end handle. It will try 4 positions in order of preference:
1. The original position
2. 50px to the left of the handle
3. 50px to the right of the handle
4. 50px below the handle, centered on the handle
cbf99f48d8