Card panel: ensured only "first" child is shown at first

The view rendered all children without selecting the current child,
meaning that all cards typically appeared on screen until a call to
"showChild" eventually hid away other cards.

The view now picks up the "first" child, or rather the first name
it finds when it enumerates the keys of the list of children. Note
that this order is not guaranteed in theory, it just happens to be
fairly consistent across runtimes...
Transition/Swipe: unknown transitions, event handlers undelegation

The transition panel crashed when a non supported transition was
requested. Unknown transitions are now properly converted to "no"
transition.

The touch event handlers that the slidepanel view attached to the
slide container are now properly unbound when the content is replaced
one way or the other to enable garbage collection and avoid side
effects.

The transition panel also triggers a "transitionend" event (was
"transitionEnd") to be more consistent with the DOM event it relates
to.