Consider a more modular approach to the project

[bartkl]

Inspired perhaps by the good design of RDF4j, I would like to have a more modular approach. For example:

• metamorph.core will contain the logic to parse SHACL to some internal representation (currently Malli)
• other namespaces can be added by ourselves or by third parties to the schemas namespace or something, from which logic for the target schemas is loaded
  • avro namespace like we have now would be an example

There's a lot to think about:

• With careful implementation using protocols one might actually make this JVM interoperable. Not sure about Malli then, though. Wouldn't it be cool if people can contribute in other JVM-compatible languages though?

Related: #50