Change Stage getter stageVideos from notImplemented to somewhatImplemented

Babysteps for `flash.display.Stage` tracetest.
Fix various Stage accessors' behavior

Specifically, `stageWidth`, `stageHeight`, `stageVideos`, and `displayState`.

Also adds a few Stage unit tests.
Remove flash_display_Stage tracetest

All remaining tests have been integrated into the Stage unit tests.
Remove wrong description of how Graphics#_lineContainsPoint works
Fix path data deserialization bug in line hit testing

@mbebenita was, of course, right about the previous code being wrong. My thinko was that this'd affect drawing, but the deserialization code for that is entirely different.
Fix handling of aliased classes and AMF deserialization of objects with AS3 classes

Makes flash_net_classes tracetest pass.
Merge pull request #1589 from tschneidereit/master

Various fixes for tracetest-covered issues
Add support for dump().

I use dump() a lot for ad hoc profiling in the browser. This patch adds
a TypeScript declaration and a shell definition.
Merge pull request #1591 from nnethercote/add-dump

Add support for dump().
Merge pull request #1598 from yurydelendik/master

Fixes several swfdec AVM1 tests
Fixes lint regressions from d6b57e8e0218ead