Enable Grover's algorithm for satisfiability problems in the PA method

[Ignaci09]

The PA method consists of finding the values of the exposed variables such that the equations of the system holds. This, and the plot of each equation, are satisfiability problems and hence can be solved by Grover's algorithm with a computational speed-up.

Use Qiskit to adapt the code to allow to use Grover's algorithm for the PA method.

[Ignaci09]

This may be followed by updating with more modern quantum algorithms.