#issue-421 supporting kt ucloud storage driver

kt ucloud storage is based on swift.
but kt customized it.
so default cloudfiles driver doesn't work for it.

so I patched 2 thigns.
1. using auth_uri variable to change auth url address.
 for example:
  currently cloudfiles driver's auth entry point is fixed. so we can't change it.
  to set auth_uri, now we can change it.

2. add ktucloud storage driver.
 It is inherited cloudfiles.py and set some parameters. 
 so it is very easy  to read.