* fixes race condition on geometry conflict calculation if performed in background process
* simplifies access to smaller buffered geometry
* adds mapping of "qm"->"m2" for UnitChoice in API usage for backwards compatibility
* extends the API to support serializing and deserializing of action_details and biotope_details
* renames biotope_extra_types into biotope_type_details on CompensationState model for convenience reasons and to match CompensationAction's action_type_details
* adds support for DELETE method for all relevant objects
* improves get_obj_from_db functionality
* drops custom compensation logic for get_obj_from_db due to improvement of base method
* adds creation tests with minimum data for intervention, compensation, ema and ecoaccount
* fixes bug where empty geometry would not be created properly using the API
* reworks key fetching from POST data, so inproperly stated keys will lead to an error for the API user, instead of silently working and use default data
* adds some logical checks for deductable_surface of eco account creation using api
* fixes bug that would have occured on creating compensations via api
* adds support for PUT and POST of Ema
* moves set_responsibility() and set_legal() from Intervention API Serializer into proper Mixins where they belong to
