Fix issue 10: NonlinearVariationalSolver does not pass linear solver parameters
Fix in Cahn-Hilliard demo for updated NewtonSolver interface
More Cahn-Hilliard fixes
Handling of PETScSNES parameters
Update PETScSNES unit test
Update unit tests for book (with careful comments in README) to match moved
parameters for nonlinear solver
Propagate parameters to wrapped solver instances
Merge branch 'logg/fix-issue-10'