Support for hierarchical module schemes

[casparvl]

As a result of a conversation with @bartoldeman I tried to run our GROMACS test on the software stack from The Alliance, but it failed because our current tests (specifically the find_modules) assume a flat module scheme.

We should think if/how we can improve this. Probably have a look at how The Alliance specifies their ReFrame tests right now.

[casparvl]

Just had a look at /cvmfs/soft.computecanada.ca/custom/reframe/config/settings.py and /cvmfs/soft.computecanada.ca/custom/reframe/checks/apps/namd/namd_check.py.

The hierarchical part is covered by loading a certain programming environment. With that programming environment, the test is then run. I might have simply had issues running the GROMACS test not because the GROMACS test is not portable, but because I'd have to adapt my ReFrame config to include the programming environments that make sense for the software stack from The Alliance. I'll give that another go once I find time...