Petsc configure

- add ASPECT_USE_PETSC configuration flag
- check if we have deal.II with PETSc if ON, Trilinos otherwise
- log info into detailed.log
- be more silent (do not list every test we find)
- do not run the testsuite with PETSc (because most tests would fail and I want to at least compile ASPECT on the tester).

We can think about adding separate tests/test-output for PETSc.