Remove support for product attributes in Android xml files.

The product attribute was never used, except in one place in Chrome that
wasn't actually needed (see https://codereview.chromium.org/1288243002).
Further, the product attribute has no compelling use case in typical
development and isn't even documented on developer.android.com (See:
http://developer.android.com/guide/topics/resources/string-resource.html)

This also updates the header comment in android_xml.py to explain the
new <plurals> feature added in https://codereview.chromium.org/1258833004

R=thakis@chromium.org

Review URL: https://codereview.chromium.org/1291173002 .

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@195 7262f16d-afe8-6277-6482-052fa10e57b1
5 files changed