Add shell option to laod shell library, this is needed for some AVM2 tests.
A few type annotations.
Fix the way we construct trait prototypes. We no longer hijack TS prototype objects and always create new ones.

This was causing some problems in XML where the old prototype object was being copied, and this patch should fix that.
Fixes to the way binary symbols are handled in ByteArrays.
Merge branch 'master' of https://github.com/mozilla/shumway into overlay
Move avm2 tests to test folder and add 'grunt test' task.
Merge pull request #1629 from mbebenita/overlay

Overlay