Merge pull request #1422 from mbebenita/nat

Keep back references in Renderables
Make `grunt avm1lib` build the TS part as well as the AS part
Remove redundant compilations from `grunt shu`

`player` subsumes the removed sub-targets.
Move AS2Utils include above Sprite include

Required for next patch to work.
Properly wire up registration and usage of SWF-exported AS2 assets as AS2MovieClip subclasses
Reinstate invocation of AVM1's flushPendingScript in `frameConstructed` event phase
Stub implementation of AS2Sound class

Doesn't do anything, but also doesn't throw any errors.
Properly create AS2 wrapper for TextField in createTextField
Stop playback in AVM1 ActionGotoFrame if no ActionPlay tag follows

Because that's what the Flash player does.
Wire up AS2Button initialization for timeline-placed button symbols
Merge pull request #1423 from tschneidereit/nat

AVM1 fixes
Match the apparent behavior of Flash when it comes to clipping masks that appear at the end of the display list.
Add option to disable clipping.
Don't overlap stage with the settings panel.
Adds a debugging canvas that can be inserted and removed via the release inspector option.
Merge branch 'nat' of https://github.com/mozilla/shumway into nat