Rewrite of cbsdk

[cboulay]

• Modularizes shmem, device communication, and API code
  • can be reused partially or wholly in other applications
• shmem always assumes Central layout (4 procs)
• modernize
• device located automatically

Still work to do

• Check why Hub1 but not NSP has packets with invalid instrument ids (nowhere to index into shmem)
• Add remaining packet types (CHANINFO, SYSINFO, etc.)
• Add remaining buffer types (Add CentralReceiveBuffer, CentralTransmitBuffer)
• Version checks on shmem layout or device protocol
• Fill out API
• More callback types
• Validate Python code that interacts directly with shared memory then use in pycbsdk