Rework complete templatedossier functionality:

* Move the files in to a subdirectory
* Split them up in to separate files
* Rework the tests (using ftw.testbrowser)
* Pep8
* Pyflakes
Templatedossier: cleanup the types.xml.

* Drop no longer existing Mail behavior.
* Fixed copy&paste fail.
Allow nested Templatedossiers.

This change should not be a probleme for existing installations, because
adding templatedossiers is protected by a separate permission, which only
the `Manager` Role owns.