Correct argument error handling for MovieClip#gotoAnd*

Plus documentation and cleanup.
Correct argument error handling for MovieClip#addFrameScript

Plus documentation.
Add unit testing setup for MovieClip

And run it in the default shell test set.
Exit shell test harness with error code `1` if at least one test failed

Makes grunt show an error message instead of happily saying that everything is just peachy.
Add framescript execution tests to MovieClip unit tests
Properly check arguments in MovieClip#gotoAnd*

With tests
Fix bug causing MovieClip#addFrameScript not to work for the last frame

With test
Make `callConstructor` a required parameter in `createAnimatedDisplayObject`

We can perfectly well add it to all call sites, and having it optional has overhead.
Merge pull request #1404 from tschneidereit/nat

MovieClip fixes and unit tests