Add tests for superposition

[fedimser]

In addition to testing arithemtic operations on basis states, now we test them on superposition states.

The testing approach is:

• Initialize each input to a superposition of two integers, with random (real) probabilities.
• Apply operation.
• Inspect state of the machine (using qsharp.dump_machine()), project it on last register and extract all non-zero basis states with their probabilties.
• Compute what would be expected state classically.
• Compare resulting superposition to the one predicted classically.

The logic to test superposition is in superposition_test_utils.py, and I used it to test correctness of some algorithms (addition, subtraction, multiplication and division).

Note that we must call qsharp.init() for each test, because these test do not release qubits.