status.py: Adds a new status class and subclasses

These status classes are intended to replace the string statuses
currently used by piglit.

They give a couple of very nice advantages, first, they can be directly
compared to each other to determine whether a status is worse than
another status. These statuses can also be compared to any object
implementing the __int__ method.

This will allow us to remove a number of special functions for sorting
representations of statuses.

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
satus: Make use of the status objects

This adds code in framework/summary.py and framework/core.py to make use
of the status classes in status.py. This makes comparisons between
statuses much simpler and cleaner

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>