Completely rewrote the Rackspace object auth routines

This was necessitated because I wanted to continue to use the same
.rackspace_cloud_credentials file for all my challenges whether they
were php-opencloud-based or pyrax-based. Unfortunately, pyrax wants
the ini file formatted a very specific way so I had to make my php
scripts conform. Plus it was nice pulling all that auth out into a
separate file that they could all include.
oops, forgot challenge5 in the last commit