Enhancements and cleanup related to star setup

[themikelau]

Mostly a cleanup of code related to the star setup. Changes include

• eos: New subroutine calc_rho_from_PT.
  • eos_idealplusrad: New subroutine get_idealplusrad_rhofrompresT.
• Enhancements to ptmass_calc_enclosed_mass
  • OpenMP parallelisation.
  • Exclude for dead or accreted particles.
  • Non-uniform weights in particle counting.
• Choice of heating kernels for heating particles around sinks
  • New subroutine heating_kernel allows uniform heating or heating with kernel softening.
• Increase number of significant figures written out by write_mesa.
• Core softening enhancements:
  • setfixedentropycore: Improve robustness and error messages for solving a flat-entropy core.
  • set_softened_core: Allow use of finer r-grid in softening region than the arbitrary gridding provided by the input stellar profile.

Changes to fileutils: get_column_labels can now find column headers that are delimited by a varying number of spaces. This fixes a bug where the stellar profile "P12_Phantom_Profile.data" cannot be read.

Wrapping code into functions or subroutines:

• Query function sink_has_heating to see if any sink particles have heating.
• Stash solving for u and T in read_star_profile to new subroutine solve_uT_profiles.

[danieljprice]

thanks Mike!