Update all workflows at once

This PR adds a button for rebuilding all workflows (writing ``definition.xml``s) and its translations (``plone.pot`` / ``plone.po``) for all discovered workflows at once:

![bildschirmfoto 2014-09-09 um 09 08 50](https://cloud.githubusercontent.com/assets/7469/4197844/34447856-37f0-11e4-9805-1b3f8305e471.png)

Closes #44