Cleanup and eliminate simplelayout.types.common dependency

This pull-request includes various cleanups and refactorings in order to eliminate the simplelayout.types.common dependency and use ftw.contentpage instead.

- Cleanup: move all page templates into a seperate folder
- Use ftw.contentpage's block views instead of s.t.common's, or use simpler implementations with custom page templates if possible
- Refactor blocks and chapter to no longer subclass on s.t.common types and use subclass ftw.contentpage types or directly AT types.
- Cleanup schemas, so that we no longer have unnecessary fields

Requires https://github.com/4teamwork/ftw.contentpage/pull/155
@maethu please take a look