Feature Request: Compose Scrambles

[DougCube]

It would be good to have a way to compose scrambles (of different formats):

1. state ∘ state => state
2. state ∘ alg => state
3. alg ∘ state => state
4. alg ∘ alg => state
5. alg ∘ alg => alg

Number 2 is the most useful in the flow of creating multi-stage solvers that start from a state instead of an alg. (Which is needed in random-state scramble generators, you generate a random state, solve it, and the inverse of the solve alg is the scramble alg.) Number 1 seems to be the most basic to include since --showpositions has a mechanism to convert algs to states anyways. Thus, having a way to accomplish 1 can give 2, 3, and 4 nearly for free. I can't think of a situation requiring number 3, but might as well. Number 5 is trivial, but listed for completeness sake.