fix inheritance problem with mixin

- a mixin should not inherit from module then it has Parameters
- Parameters in mixins must be complete, not just overrides
- check precedence of read_<param> or handler

Change-Id: I72d9355a1982770d1a99d9552a20330103c97edb

secop_psi/sea.py

@@ -359,6 +359,8 @@ class SeaModule(Module):
             else:
                 pobj = Parameter(**kwds)
                 datatype = pobj.datatype
+            if name == 'cc' and key == 'value':
+                print('cc.value: %r %r' % (kwds, pobj))
             attributes[key] = pobj
             if not hasattr(cls, 'read_' + key):
                 def rfunc(self, cmd='hval /sics/%s/%s' % (sea_object, path)):