ENHANCE: Performance of Isomorphism

Add a documented global function `AsAutomorphism(sub,autom)`, replacing the
local `asAutom`/`asAutomorphism` helpers that were duplicated in
`AutomorphismGroup` and `PatheticIsomorphism`.

Factor the normal subgroup class stabilization into a local function
`stabilizeSubgroupClass`, using permutation action and set stabilizer
instead of `OrbitStabilizerAlgorithm`, lower the index threshold to 10^3 for
using it.

Keep the inner automorphism group as permutations for the condition search.

When finding the isomorphism through multiple orbits and stabilizers, reduce
the number of generators.

Clean out some dead code and careless double computation.

Author: hulpke