Threaded server

[hatlabcz]

Ported over the code for threaded server that uses the router/dealer ZMQ pattern

• Server can now handle request from multiple clients concurrently, with a per-instrument lock.
• Client is changed to the the dealer socket to work with the router socket on the server, but still single threaded.
• These changes means the following behavior:
  • In a single client process, commands are still always blocking (so instrument calls still run one after another)
  • From different client processes, commands on the same instrument are also blocking . (This is intentional for safety, since not all hardware can safely handle simultaneous commands; calls will still be handled in a queued way as long as timeout is long enough.)
  • From different client process, commands on different instruments can now run fully in parallel.
  • These can be tested with instrumentserver/testing/test_async_requests/demo_concurrency.py

Other changes

• Changed default unit for timeout from miliseconds to seconds to match with QCoDes
• Made proxy.Client cache instrument blueprints

[marcosfrenkel]

This looks excellent!