Issue #205: rename SwipeTouchListener class

Rename it to SwipeDismissTouchListener, since that name indicates more
of what animations it will perform. Also rename undoAnimation back to
resetAnimation, because it is easier to say.
Issue #205: allow swiping only in some situations

Add a isSwipeDismissable method to the OnSwipeDismissListener for
checking whether or not the swiped view is dismissable. Don't allow
swiping when the user doesn't have an accounts. Furthermore, don't
permit it on subreddits that don't have sidebars like front, all,
and random and those that are search results.