Add a new bindings2/scripts directory for Dart bindings

Add a new bindings2/scripts directory for Dart bindings

These bindings were developed over the last 2 weeks on:
https://github.com/eseidel/skydart
They started as copies of the Dartium scripts (aka dart/tools/dom):
https://code.google.com/p/dart/source/browse/#svn%2Ftrunk%2Fdart%2Ftools%2Fdom
Which in turn started as a forked copy of Blink's
binding generation scripts from some years ago.

This is still way more python than we need to generate
bindings for SkyDart, but it's a start.

Reviews were done for many (but not all) of the patches.

I'll add the bindings2/ code and build system wiring
in further patches. Landing the new directories one at a
time so that it's easier to read through.

R=abarth@chromium.org, jamesr@chromium.org
BUG=454613
Committed: https://chromium.googlesource.com/external/mojo/+/eb926e70c355f19b418e3ac0e71b4778afbf116e

[abarth-chromium, 2015-02-12 20:22:22]

LGTM

Please file a bug about improving these scripts to have less V8 and Dartium
crazy.

[eseidel, 2015-02-12 20:22:42]

Committed patchset #3 (id:40001) manually as
eb926e70c355f19b418e3ac0e71b4778afbf116e (presubmit successful).