New yaml character format (#337 from TheTerrasque/feature/yaml-characters)

This doesn't break backward compatibility with JSON characters.

server.py

@@ -46,7 +46,8 @@ def get_available_prompts():
     return prompts
 
 def get_available_characters():
-    return ['None'] + sorted(set(map(lambda x : '.'.join(str(x.name).split('.')[:-1]), Path('characters').glob('*.json'))), key=str.lower)
+    paths = (x for x in Path('characters').iterdir() if x.suffix in ('.json', '.yaml', '.yml'))
+    return ['None'] + sorted(set((k.stem for k in paths)), key=str.lower)
 
 def get_available_extensions():
     return sorted(set(map(lambda x : x.parts[1], Path('extensions').glob('*/script.py'))), key=str.lower)