Define and describe CI common architecture

A common CI infrastructure is often emerging as one of the main derived from the consortia setup of the design consortia.

Maybe this is not a top priority in terms of documentation for system CDR, but it is certainly important content that should be an integral and fundamental part of system level plans and design.

Proposal is to extend SDP Software Management C&C (or develop something equivalent, personally I would prefer keeping the SEI style) such that it can be used as a shared CI architecture description for different SKA software sub-systems.

This should:

• Show how the CI system would interact with relevant SKA software systems. Likely all via artefact repository.
• Decompose CI infrastructure a bit, clarifying that we need build servers (possibly multiple flavours for access to specialised hardware), and possibly dedicated license servers
• Show more explicitly that we want to make certain build artefacts (such as test reports and built documentation) available to developers.
• Might want to add deployment diagrams, showing how the different components might be spread across different SKA sites and the cloud (this should likely remain a variability, i.e. illustrative for the moment).

https://docs.google.com/document/d/17vTU4IGJpUc_QEhJzxOgC_R4GHYHJ3DAmEagJ4sZTGQ/

Relative to the acceptance criteria - somewhat partial points on showing interaction with other SKA elements (left mostly open, but that's likely enough), but CI decomposition and user interfaces have been fleshed to a pretty high standard. Haven't really looked at deployment, but this might not be critical right now. An extra data entity view was added.