Create a SerializableComparable class derived from the Serializable
class.

Added the following functions to the SerializableComparable class:
  '__eq__'
  '__ne__'

Disable the '__hash__' function in the SerializableComparable class as
some derived classes are mutable.

Use the SerializableComparable class in hardware.py and
extensions/base.py

This should make unit testing users of the class easier when doing a
self.assertEqual() or self.assertNotEqual()

Added some initial unit testing for encoding.py

Change-Id: If0f14b3bfe7f1391f65dd730a16a534afed0da82