* add localization utilities:
- add locmanager to support extract, update, remove, list using pybabel
- add po2csv/csv2po conversion with translate-utils
- docs: add localization.rst to manual!
* add language switch header (via header.html) to all pages if more than one locale is present.
* localization: wrap more text strings in templates in existing templates
* docs:
- document `wb-manager i18n` commands
- mention `<html lang>` setting
- include csv example
- add info about adding localizable text in templates
* add localization to CHANGES
