Change timestepping structure in run_part

[jcurtis2]

run_part both controls the timestepping and calls all the functions individually to progress an entire simulation (from time $t=0$ to $t=t_{\rm max}$. Instead it would be good to be able to run chunks of time, implemented with run_part_timeblock which will simulate from time $t$ to $t + t_{\rm progress}$ (or other specified interval), and a single timestep, implemented with run_part_timestep which runs from time $t$ to $t+\Delta t$.

[mwest1066]

Looks good to me! I left suggestions about separating out the CAMP arguments on a fine-grained level. This isn't required but I think it makes the code a bit clearer because it highlights what is actually different with CAMP. It might also make it simpler with future modifications because we only need to change one place rather than two.

[mwest1066]

Would it be cleaner (and safer for future modifications) to separate out the CAMP code on a more fine-grained level? This would match what we do below in the argument variable definitions. For example:

Suggested change

	#ifdef PMC_USE_CAMP
	subroutine run_part_timestep(scenario, env_state, aero_data, aero_state, &
	gas_data, gas_state, run_part_opt, camp_core, photolysis, i_time, &
	t_start, last_output_time, last_progress_time, i_output, &
	progress_n_samp, progress_n_coag, progress_n_emit, progress_n_dil_in, &
	progress_n_dil_out, progress_n_nuc)
	#else
	subroutine run_part_timestep(scenario, env_state, aero_data, aero_state, &
	gas_data, gas_state, run_part_opt, i_time, t_start, last_output_time, &
	last_progress_time, i_output, progress_n_samp, progress_n_coag, &
	progress_n_emit, progress_n_dil_in, progress_n_dil_out, &
	progress_n_nuc)
	#endif
	subroutine run_part_timestep(scenario, env_state, aero_data, aero_state, &
	gas_data, gas_state, run_part_opt, &
	#ifdef PMC_USE_CAMP
	camp_core, photolysis, &
	#endif
	i_time, &
	t_start, last_output_time, last_progress_time, i_output, &
	progress_n_samp, progress_n_coag, progress_n_emit, progress_n_dil_in, &
	progress_n_dil_out, progress_n_nuc)

[mwest1066]

Could do a similar separation of just the CAMP arguments here.

[mwest1066]

Also here we could separate out just the CAMP arguments.

[mwest1066]

Could also separate out the CAMP arguments here.