Reduce features to required minimum

[alexlawrence]

At the moment there is almost only one consumer of this library (https://github.com/efacilitation). Therefore the main development should be concerned about the exact needs of this consumer. In order to reduce complexity, to reconsider actual requirements and to think about possible refactorings all not actively used features should be completely removed.

[alexlawrence]

Removed all up until now not required features.