[Dev] API change: Kind.getAttribute()

[Andi Vajda]

Kind.getAttribute(name) now raises an AttributeError if there is no attribute 
by that name.

I changed all relevant code accordingly, still there are two unit tests which 
I had to disable since they still fail:

   - TestMail.py because of bogus attribute names in cloud endpoints
   - TestItems.py because ? I suspect the parcel loader to handle reference
     attributes to self well

Andi..