Replaced with LinearSolver::Options::elimination_groups. Change-Id: I7c07542ec19279a35ddf6da498d417a79395c77f
Change-Id: I0ec85218e82d1714279d41f7635104d480fb91c3
unnecessarily complexity in the structure of linear solvers and preconditioners. This is the first step towards cleaning up the Preconditioner interface. 2. Minor tweaks and cleanups to the various linear solvers.