Add Hadamard test

[blolt]

This PR addresses issue #72.

Description of changes: This PR adds the Hadamard test to the library's implemented algorithms, with an optional flag that can be toggled for estimating either the real or imaginary part of the controlled unitary. An extension could be implementing the modified hadamard test, which could possibly make use of Amplitude amplification (Issue #100).

Testing done: Unit tests and notebook created.

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[blolt]

Closed this as it was the wrong commit. See the correct commit in this PR here: #158.