Wrote starting doc about hydra-python-core library

[de-sh]

Solves #54

This is a starting doc mostly copied from the relevant repo README.

Would love to hear opinions about how to better present same.

[Guttz]

I guess this is also useful, but what I had in mind with #54 was detailing how to use Core to interact with an apidoc. Ex.:

To initialize:
api_doc = doc_maker.create_doc(apidoc)

To get a list of Supported Properties:
api_doc.parsed_classes[collection_type][class].supportedProperty

To get a list Supported Operations:
api_doc.collections[endpoint][collection].supportedOperation

Along other basic actions which are useful when interacting with the apidoc. We currently have some different materials that cite doc_maker like Chris and Akshay's posts at
https://www.hydraecosystem.org/seasonofdocs-2019.

[de-sh]

Awesome, getting to it!

[xadahiya]

We probably want to main sections here.

• A section explaining how the library can be used to write new a Hydra Vocab
• Another section explaining how the library can be used to interact with the APIDoc just like @Guttz said.

[de-sh]

We probably want to main sections here.

• A section explaining how the library can be used to write new a Hydra Vocab

Ok, so this will be more like in the tutorial sense, like how a "make your own app" article goes in most framework documentation.

[xadahiya]

Closing this. @de-sh Please make a PR once you've something substantial