TextView - fix ClickableSpans always triggering on touch up

* introduce GestureDetector to TextView
* completely remove link click functionality from
  LinkMovementMethod (the interface does not state it
  provides click functionality)
* intercept onSingleTapConfirmed and trigger onClick on the
  link if it exists (simplified duplicated functionality)
* renamed a bunch of LinkMovementMethod variables because
  eyes hurt

Bug: 23692690
Change-Id: Idaf3f3391328207f42521235fb5deb1a11c66aaa