Fix duplicated strings in ADMX templates.

Also fixed the generated <string> IDs, which can't contain "."
characters.

BUG=chromium:429117

Review URL: https://codereview.chromium.org/702793003

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@181 7262f16d-afe8-6277-6482-052fa10e57b1
Set the MAXLEN/maxLength attribute for strings in ADM[X] templates.

This allows strings and JSON blobs in the registry and GPO
objects to have a length longer than the default of 1023 characters.

BUG=chromium:428340

Review URL: https://codereview.chromium.org/687073003

git-svn-id: http://grit-i18n.googlecode.com/svn/trunk@182 7262f16d-afe8-6277-6482-052fa10e57b1