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/testcmd.py

@@ -38,12 +38,14 @@ class TestCmd(Module):
              result=StringType())
     def arg(self, *arg):
         """5 args"""
+        self.tuple = arg
         return repr(arg)
 
     @Command(argument=StructOf(a=StringType(), b=FloatRange(), c=BoolType(), optional=['b']),
              result=StringType())
     def keyed(self, **arg):
         """keyworded arg"""
+        self.struct = arg
         return repr(arg)
 
     @Command(argument=FloatRange(), result=StringType())