add parallel direct solver test
Merge pull request #78 from tjhei/direct_solver_test

add parallel direct solver test
be silent about finding tests
add configuration parameter to find PETSc

We need to check if deal.II has PETSc support and add the compile flag
if we want PETSc.
write into detailed.log if we have PETSc
don't run the testsuite with PETSc
include PETSc string in build info on tester
add support for PETSc tests
ctest: put PETSc in build name
rename USE_PETSC to ASPECT_USE_PETSC
remove commented code