ADDED: Use RCM by default in SS solvers
ADDED: Use RCM by default in SS solvers

Direct SS methods that use sparse LU decomposition make use of RCM by
default.

anubhavvardhan/qutip,zasdfgbnm/qutip,qutip/qutip,cgranade/qutip,zasdfgbnm/qutip,anubhavvardhan/qutip,qutip/qutip,cgranade/qutip