[NaCl SDK] Support multiple configs

[NaCl SDK] Support multiple configs

Slightly modified from noelallen's codereview.chromium.org/10823177.
My changes: style nits, as well as fixing pnacl builds
original CL description follows:

This CL adds support for Debug and Release configs.
It moves functions that require knowledge of the Makefile to make_rules.py and
keeps functions that require understanding of the DSC files in
generate_make.py.

It adds a 'config' parameter to the embed in common.js.
Updates all index.html files to support the new config parameter.

make_rules.py has been converted to a class. This allows the object to persist
state about the build which allows us to remove knowledge of the make rules
from generate_make.py.

BUG=none
TBR=noelallen@chromium.org
NOTRY=true

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=150289

[commit-bot: I haz the power, 2012-08-07 06:46:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/binji@chromium.org/10828187/1

[commit-bot: I haz the power, 2012-08-07 06:46:21]

Change committed as 150289