Lazy load parameter objects

Only create parameter objects once we try to access an
operations parameters.

Empirically, for ec2, this saves about 50 milliseconds
of time because we aren't creating parameter objects
for other operations we won'd use.
Lazy load operation objects

As part of this change, I've removed the setattr()
calls that map the operation objects to method calls.
I think this feature makes sense, but perhaps in a higher level
(or separate) interface.
Add debug message when a service object is created