Changes to SSAFD convergence failure recovery code.

1.  In event of effective viscosity convergence failure, add first-try
strategy of under-relaxation.  See issue #282.  Default coefficient is 0.8,
which has no particular justification.

2.  Separate first-try strategies.  If effective viscosity then see above.
If KSP diverged then try ASM solver options.

3.  write_system_petsc() signature now allows different names.