[WIP] Enable PETSc + MUMPS
This MR changes PETSC to build its own MUMPS library:
- It works for me
- MUMPS requires a Fortran compiler and in order to make MPI pick up the Fortran specific libraries, i had to add that language to Nektar++
- Now PETSc compiles its own MUMPS, scalapack and scotch
- Building PETSc with metis did not work because that will conflict with our modmetis library
- Pointing PETSc to Nektars scotch install was not successful and i have no idea what happens when Nektar++ and PETSc both use their own versions