Divide feature files

After a while searching saw that in most cases each feature file as only 1 user 

**Needs**:
- [x] ezsystems/ezpublish-community#142
(already have the "update" feature)

So this refactor is to reflect that:
- [x] Divide features per users (ie: administrator/anonymous)
(for ContentTypeGroup we won't need more than an administrator for the positive tests and an anomymous for the unauthorized ones)
- [x] Update features descriptions