Implement the face semigroup of a hyperplane arrangement and provide a custom class for the algebra

[tscrim]

The face semigroup algebra of a hyperplane arrangement is implemented as an instance of the FiniteDimensionalAlgebra. We should first provide a direct implementation of the face semigroup as a stand-alone parent. Then using that, we should implement a custom class for the algebra (possibly a subclass of FiniteDimensionalAlgebra, but the most likely candidate would be as a subclass of CombinatorialFreeModule whose basis is the semigroup). This will give it more features and a direct link to the hyperplane arrangement.