Add a function apply_symmetry

[apozas]

This would be useful for imposing other symmetries such as invariance under permutation of parties. In the same spirit of what happens inside of apply_inflation_symmetries, it would take a permutation of the list of generating monomials, apply it to the moment matrix, and update the necessary objects. Then we could even make apply_inflation_symmetries to call this function internally.

[ecboghiu]

We could add an extrasymmetries flatg to generate_relaxation in the format of permutations of the generating set or, maybe ask the user to give a new orbits dictionary that encodes their symmetry.

[apozas]

This should have been addressed in #160. If you think this is not what was intended in this issue, please reopen.