Translation script: add option for output formats

Option is not really expected to be used as the only output format we'll
be generating right now is POT format, but it's still handy to have.
Translation script: walk whole tree

This adds the ability to walk the whole Git repo looking for HTML and
JS files to extract translation strings from. Next up: creating app.pot
files in appropriate places (src/angular-app/[site]/[app]/lang/app.pot)
and en.po files alongside the app.pot files.
Convert (by hand) the fa.po to fa.json
Merge remote-tracking branch 'origin/localization' into localization