Parseable

- fix corner case for some schemas with static string as value
- added unit tests

- more exports from schema to make imports easier

- parseables inner data is not expanded by default anymore, so you can check parseables and subparseables types in the data structures.
- the new expand function will get rid of parseables in a data structure and recursively replace them with their data
- updated checks and documentation
- added a license file

- data is accessed via items, not attributes
- written base classes depending on schema type
- base classes use abc
- more documenation
- more tests

First beta release, essential concepts implemented