Add Python templating engine Jinja2 to third_party

A templating engine will make it easier to create/maintain the python code generators in Blink (e.g. https://codereview.chromium.org/14905002/)

BUG=

Review URL: https://chromiumcodereview.appspot.com/14761007

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 88a0c56a390c51cd4414c027820100069c4ba78d
29 files changed