Restructuring

[floybix]

Fixes #23 Fixes #46

• Removed regions completely. Comportex networks now consist only of layers.
• Layers are constructed in unembedded state, then embedded in a network.
• Layers receive signals - consisting of SDRs - from surrounding layers/senses.
• core namespace now largely abstract and separate from layer implementation.
  • it subsumes what was the protocols namespace.