Added lazy lookup of attributes from parents for ParticleType objects

mrdna/arbdmodel/__init__.py

@@ -341,7 +341,12 @@ class ParticleType():
     def __init__(self, name, charge=0, parent=None, **kargs):
         """ Parent type is used to fall back on for nonbonded interactions if this type is not specifically referenced """
 
-        self.name        = name
+        if parent is not None:
+            for k,v in parent.__dict__.items():
+                if k not in ParticleType.excludedAttributes:
+                    self.__dict__[k] = v
+
+        self.name   = name
         self.charge = charge
         self.parent = parent