Ref #2059
- Refactor appProxy into class that is instantiated per App
- Check for permissions before doing proxied filter/helper calls
- Add all currently existing api methods, let api check for permissions
- Basic unit tests for filter and helper register/deregister
- Adjusted proxy api method existence unit tests
first 10 % of #2124
- added initial version of JSON API tests
- renamed error.errorCode to error.code
- renamed tags.all to tags.browse for consistency