organize catalog game classes with section headers for better readability

Author: edwardchalstrey1

src/pygambit/catalog/catalog.py

@@ -92,6 +92,11 @@ def __init_subclass__(cls, **kwargs):
         cls._extract_metadata_from_game(cls._cached_game)
 
 
+############################
+# Catalog games from files #
+############################
+
+
 class PrisonersDilemma(CatalogGameFromFile):
     game_file = "pd.nfg"
     description = "Prisoner's Dilemma game."
@@ -104,6 +109,11 @@ class TwoStageMatchingPennies(CatalogGameFromFile):
     citation = "Example citation for Two-Stage Matching Pennies."
 
 
+##########################################
+# Catalog games defined programmatically #
+##########################################
+
+
 class PrisonersDilemmaTestgame(CatalogGame):
     title = "Test Prisoner's Dilemma"
     game_type = "nfg"