Implements MovieClip#currentFrameLabel and MovieClip#currentLabel
fixes #477, makes all MovieClip#currentXXX properties work as intended, implements gotoAndStop/Play with scene target
break out of loop when done
makes lint happy
Tests for PR #478
Merge pull request #478 from claus/framelabel

MovieClip#currentFrameLabel, currentLabel, currentLabels, also wrt Scenes