Centralize tools build target's references

Mostly, this reduces references to `src/utilities.ts`, which will come in handy later.
Introduce new `base` TypeScript build target combining all utilities/services

... and include it's `d.ts` output in the other build targets' references files. Reduces compile time of, e.g., `grunt player` by about 20%.
Move all files included in the `base` build target into `src/base` and combine them during building
Combine files in the `tools` build target into one output file and reference the resulting d.ts file in other build targets
Combine files in the `swf` build target into one output file and reference the resulting d.ts file in other build targets
Combine files in the `avm2` build target into one output file and reference the resulting d.ts file in other build targets
Combine files in the `avm1` and `avm1lib` tsc build targets into one build target and output file and reference the resulting d.ts file in other build targets

To make this work, I had to untangle the dependencies between `flash` and `avm1lib`: they're now both using `d.ts` files for the few members of the respective other build target that they really depend on.
Combine files in the `gfx` build target into one output file and reference the resulting d.ts file in other build targets
Combine files in the `flash` build target into one output file and reference the resulting d.ts file in other build targets

Combines several hundred output files into one.
Update `shu` build target to build all required targets in order to get a working player

Plus bits and pieces that needed fixing.
Merge pull request #1432 from tschneidereit/nat

Combine build output into a set of js files per build target and letting targets depend on each other
Fix native binding of AS2Utils class

I regressed this while untangling the `avm1`, `avm1lib` and `flash` build targets.
Merge pull request #1433 from tschneidereit/nat

Fix native binding of AS2Utils class
Add `_root` and `_level0` properties to AS2MovieClip

These should be invisible to script in that `hasOwnProperty` should return false for them, but for now this is ok.
Merge pull request #1434 from tschneidereit/nat

Add `_root` and `_level0` properties to AS2MovieClip
Merge branch 'nat' of github.com:mozilla/shumway into nat