i18n - extracting new, pulling from tx

fixes #8874 - rework POT/PO updates for gettext 3's edit.po

3.1.13 adds an intermediate .edit.po file alongside each .po, which is meant
to be kept outside of SCM and updated by users, whereupon it's merged back into
the .po on the next rake gettext:find execution....

fixing transifex domain in .tx/config and scripts

fixes #2368 - finishing transifex.com integration

Feature #2368 - i18n integrating Transifex