Due to a bug in the version of subgroup_search using baseswap
to perform the base changes, the way basic stabilizers are
obtained is now via the stabilizer() function. The function
_insert_point_in_base was remove from sympy.combinatorics.util
since it's not needed right now.
Also, made the incremental Schreier-Sims algorithm exclude the
identity element as a generator and wrote some more tests