Establish the SKA SDP Processing Function Library

Processing functions will provide the building blocks for future SDP pipeline development, therefore establishing how these will be organised, discovered, developed, and maintained early is critical to the future sucess of the SDP product.

Setting this up now will set an initial minimum standard which for how we develop processing functions in future both in terms of organisation and software engineering quality.

• Define and create a repository structure with initial directory layout and infrastructure to provide basis for future SDP processing function development. The intention is that this will either become the single SDP processing library (preferred) or alternately a template that others should follow if the case can be made that it is better to have more than one library.
• This should contain a simple, well documented, tested, example for others to follow for how to develop and integrate processing functions in future and establishing the minimum software quality standards for doing so.

Existing solutions were investigated, and the summary is on the confluence page: https://confluence.skatelescope.org/display/SE/SPO-1371+--+Processing+function+library, where there is also a proposal for the processing function library regarding structure, what it should contain and desire behaviour. The example of a processing function using this proposal is located here: https://github.com/KAdamek/sdp_PF_library