Remove unused swf/_renderer.js file

One can always look at it on github or in the history to see how things used to be done.
Remove swf/*-exports.js files

These were only needed to satisfy the closure compiler, and we'll have to come up with something else to make that workable on tsc-compiled code, anyway.
Remove obsolete swf/config.js file

The values this sets aren't used anywhere, anymore.
Add license to gfx/stage.ts file
Moved contents of avm2/global.ts into utilities.ts and removed the former

This stuff is useful for all modules.
Add declaration of Uint8ClampedArray to utilities.ts

Missing from tsc's lib.d.ts.
Boilerplate for TS module for the SWF parsing stuff, plus converted swf/bitmap.js to .ts
Merge pull request #1328 from tschneidereit/nat

Porting src/swf to TS, part 1: bitmap tag handler. rs=yury