Python class to represent metadata data model

A Python class to represent the task metadata that can be loaded an OSSR entry, passed through user interaction steps to select data and resources and finally passed to synchronous/asynchronous worker to execute the task.

Just a simple set of classes that map the data model described in the metedata schema to Python classes that can be included in all our other components.

I have briefly looked at code generators, but given the simplicity of the data model they are not worth the overheads. Simpler just to transcribe the data model to classes with properties manually.