Backends

[alecandido]

Far far from completion...

[alecandido]

Despite a few complications, the TCP client-server pair is ready.

Now, hooks should be added, such that it can be used to execute circuits and retrieve the results:

• on the client side, the execute method should actually take a circuit (for the time being, not an initial state or anything else, to keep it simple) and return a state
• on the server side, an external function/struct should be able to hook into the listener, and handle execution requests

This last mechanism will be exposed in the Python API as well, and on top of that it should be pretty simple to construct the NumPy backend (only executing circuits, not any other manipulation, for the time being).

As in #6 the goal was to represent a QFT, now the aim is to execute it, and return the state vector (with a roundtrip Python script - qibo-core - Python backend).
More features in further PRs.