Major rework to enable rebuilds of the platform from single sf-build call
- Change the way that sources and system model are selected: now property based
- Split sources.csv to have publicly available http repos only; internal repos are in sources_rnd.csv
- System model output in BOM renamed to system_model.xml rather than canonical_system_definition_{config}.xml to make reuse predictable
- Public property configuration public_override_props.ant.xml now used.
- Fix all exports to run based upon configuration specified (no export configuration makes SBS assume RVCT is being used, which is not available to all)
- sf.production.build MUST be defined and TRUE to enable production build properties, public config is DEFAULT behaviour
