Improve PETSc interface

src/algebra/CMakeLists.txt

src/algebra/LinearSolver.cpp

src/algebra/PETScUtils.cpp

src/algebra/PETScUtils.hpp

src/utils/CMakeLists.txt

src/utils/PETScWrapper.cpp

src/utils/PETScWrapper.hpp

src/utils/PugsUtils.cpp

tests/mpi_test_main.cpp

tests/test_main.cpp