Class PrefsProxy

      object --+    
               |    
debug.debugmixin --+
                   |
                  PrefsProxy

Dictionary-like object to provide global prefs to a class.

Implements a dictionary that returns a value for a keyword based on the class hierarchy. Each class will define a group of prefs and default values for each of those prefs. The class hierarchy then defines the search order if a setting is not found in a child class -- the search proceeds up the class hierarchy looking for the desired keyword.