Patch User while setting up the other models

The User patching is partly work previously accomplished via the
UserIsPilotPatch middleware and partly the get_pilot_name() function moved
from Checkout to User (which is where it really makes more sense).
Remove Pilot custom field since User field is fine

The point of the PilotModelChoiceField was to override the default label (since
User's default _unicode__ was not desirable). Now that User.__unicode__() will
provide pretty output, we don't need to use the custom choice field.
Use name properties patched into the built-in User
Ensure both first and last names are set
Verify behavior of new functions in models.py
Update method of getting each pilot's full name
Remove old User model patch implementation
Delete uneeded middleware for User patching