Made sure co-moving Sod shock is run for the same amount as (re-scaled) time as the non-co-moving version.

Added derivation of comoving Euler equations to cosmology theory document.

See merge request !590

Eagle cooling

See merge request !593

Declared all the cooling tables sizes as compile-time constants. Renamed many variables. Clarified CGS nature of many variables.

Fixed typo in Zeldovich run script.

See merge request !693

Correctly interpolate the metal heating table in all cases. Add interpolation functions ignoring the x-dimension. Move the metal species as the first element in the table.

Moved the temperature interpolation function to the cooling_rates file. Improvements to the interpolation functions.

Add function to clean-up the memory allocated by the cooling routines. No more memory leak in the cooling rates test.

Add GNU style long command line arguments

See merge request !689