Mpi omp support

[hiker]

This PR adds configuration settings that enable/disable MPI and OpenMP to BuildConfig.

This means that an application can now specify that it should be compiled with OpenMP, without having to specify compiler-specific OpenMP flags - the Compiler object will get the information from the BuildConfig if it should add the flag or not.

Similarly, if an MPI build is requested, the tool repository will return an MPI enabled compiler (but the user can always overwrite this by hand-selecting a compiler explicitly).

Note that the MPI compiler wrapper added here will get a nicer (decorator-based) implementation in the next PR, I just tried to keep the PRs small. This PR is still quite big, but that's because I made the MPI and OpenMP settings mandatory (imho it makes sense to get the user to specify what exactly they want). The CLI defaults both to False. Additionally, I started to fix the line length (according to the discussion in #323