Refactor Building Block Register scope

[rob-metalinkage]

top level should just reference sub-registers. Create an OGC SWG published bblocks and pass governance to Joanna, and link to incubator.

we should perhaps deprecate "unstable" and move all these elements not formally owned by a SWG to "incubator" - would need to propagate to 3D CSDM application.

Need to link all BBlocks to SWG (via Rainbow - and make sure that integrating the register.ttl creates a back link from the SWG to the BB in the Rainbow..

[rob-metalinkage]

Basic design proposal diagram now in bblocks "About" description.

https://opengeospatial.github.io/bblocks/register/