Builder supports custom classes, custom classes must be inside a ModuleScript within the search range of the descriptor, and must return a field called
new acting as the constructor.
By default, the module finds custom classes under a folder called
CustomClasses parented to the root of the Builder ModuleScript.
Descriptor has a field,
Descriptor.CustomClassesLocation that can be set as a alternative custom class search path, it overrides the default search path.