Consistency tweaks/i18n review

* Make wording consistent with other extensions and core
* Remove Title Case
* Use {{int:..}} syntax
* Delete i18n/de-formal.json because it is widely a dupe of de.json
** Hint: Only translate messages to de-formal where is a difference
(Du->Sie)
* Fix license-name key per LICENSE file
* Message documantation added

Change-Id: I8982cb7e157420e2d4b559cbb0b1a9586674a98c