Changes

Changed sqrt_Ri_zm to Ri_zm in preparation of changing the exponent for calculation of invrs_tau_wpxp_zm in mixing_length.F90 - CLUBB ticket #1102 (#1110)

BIT_CHANGING! Changed sqrt_Ri_zm to Ri_zm in preparation of changing the exponent for calculation of invrs_tau_wpxp_zm in mixing_length.F90 - CLUBB ticket #1102
Changes in input/stats/all_stats.in, src/CLUBB_core/advance_clubb_core_module.F90, src/CLUBB_core/mixing_length.F90, src/CLUBB_core/stats_variables.F90, and src/CLUBB_core/stats_zm_module.F90
Ri_zm was added to input/stats/standard_stats.in

BIT_CHANGING! Removed Richardson_num and all corresponding code - CLUBB ticket #1102 (#1111)

This commit is BIT_CHANGING because:
1. the output field Richardson_num was removed.
2. Since the flag l_use_shear_turb_freq_sqd was removed, the variable shear_sqd is now always written to disk. That means previously, the outputted field shear_sqd was 0 everywhere whereas now it is not anymore. The calculation of shear_sqd within CLUBB did not change!
- Removed mentions in input/stats/all_stats.in and standards_stats.in
- Removed mentions in src/CLUBB_core/stats_variables.F90 and stats_zm_module.F90
- In src/CLUBB_core/advance_helper_module.F90 removed mentions to [i]Richardson_num[_clipped], as well as l_use_shear_turb_freq_sqd, l_Richardson_vert_avg, and turb_freq_sqd sinc those are only used for calculation of Richardson_num.