utils for 1.5 compatibility in migrations

added the user_model_label to allow south to refer to the user model in the migrations files.
converted initial migration to use custom user model 

imported the new user model label and then used it to enable the migration to handle using the custom user model.
update useing 1.5 compatibility fixes

same as 0001
update using 1.5 compatibility fixes

same as 0001 and 0002
added settings import so that getattr works
Merge pull request #50 from Jumpstartz/master

Migrations fixed for 1.5 custom user model