add new feature json crud feature

[suessmma]

Hi,
I'm creating some new features to create a full functional crud-server with json data files and models from the schemas of the openapi.yaml. In Detail:

Automatic generation of json-data files using the example values
Automatic generation of models from the schemas in the yaml-files
Automatic generation of services for creating, updating, deleting and viewing the respective model in the corresponding json file
Overwriting of automatically generated files, if concrete file exists in template folder
Checking for mandatory fields in the Model from yaml file