Add whitelist support to repack.

- Added ability to filter out resources by specifying a file that contains
  a list of resource id whitelist.
- Fixed lint errors in data_pack.py, data_pack_unittest.py and repack.py
- Added tests for RePack()

BUG=338759
R=newt@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/217273003

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@158 7262f16d-afe8-6277-6482-052fa10e57b1