Example Hermes-2 2d turbulence simulation

Quickstart:

1. Use your package manager (or module system) to install some MPI package, FFTW, and CMake.
2. Check submodules are downloaded with git submodule update --init --recursive.
3. Compile by running ./build-hermes-generic.sh. Uses CMake, and compiles BOUT++, which also downloads and installs SUNDIALS.
4. Run the simulation with run-example.sh. The script uses 4 MPI processes - the run command in the script is 1 line, so if you want to use a different number of cores, etc. either edit the script or copy/edit the line.
5. Create an animation of the results by running ./animate.py. As written writes the animation to animation.gif. Commented out line in the script shows an interactive animation instead.
   • To use this script, need to install the xbout package with either conda or pip.