Easybuild support

[LourensVeen]

Since we run on HPC a lot, we should have EasyBuild support. @SimonPinches did a bunch of work in this direction and submitted a PR, but that got stuck. He also ran into a bug in the MUSCLE3 build system (#169).

It seems that EasyBuild expects a fairly dumb build system that it then tells what to do (e.g. make -j, CFLAGS with additional optimisations, etc.), and that our smarter system isn't a great match. Perhaps we could add some extra targets that disable the automatics to help with that.

We should

• Create an easyconfig for MUSCLE3 and any dependencies needed
• Make any changes to the build system needed
• Figure out a way of testing this before or during a release