Replaced get_all_subs_[type] function by get_all_subs_satellites_by_type(sat_type)
Enh: refactored get_all_subs_satellites_by_type
Replaced fill_potential_[type] functions by fill_potential_satellites_by_type
Merge pull request #1222 from ReAzem/get_all_sub_satellites_by_type

Small refactoring in realm.py