Support setting linesearch parameters for PETSc 3.3

Setting OpenCMISS linesearch options had no effect with PETSc 3.3,
as PETSc 3.3 changed the way linesearch options were set and the old
PETSC_SNESLINESEARCHSETPARAMS is no longer available.

This adds wrappers for the new SNESLineSearchBTSetAlpha and
SNESLineSearchSetTolerances routines, and calls them using the
OpenCMISS linesearch settings.
Merge pull request #180 from adamreeve/linesearchparams

Support setting linesearch parameters for PETSc 3.3