simplify the request / response format document
simplify the request / response format document

This document previously existed to explain how to use either
application/json or application/xml with Nova. It's mostly confusing
in it's current state, and we're correctly defaulting to
application/json on request and response now.

Just remove most of what's confusing, users don't need to send
headers, we only do one thing now.

Change-Id: I597aeab73f1075f400f053016b4ea7bda01893a5

jianghuaw/nova,gooddata/openstack-nova,Juniper/nova,cernops/nova,rahulunair/nova,jianghuaw/nova,cernops/nova,Juniper/nova,alaski/nova,gooddata/openstack-nova,openstack/nova,mikalstill/nova,sebrandon1/nova,dims/nova,rajalokan/nova,Juniper/nova,gooddata/openstack-nova,mikalstill/nova,cloudbase/nova,jianghuaw/nova,gooddata/openstack-nova,sebrandon1/nova,vmturbo/nova,CEG-FYP-OpenStack/scheduler,vmturbo/nova,klmitch/nova,rajalokan/nova,vmturbo/nova,klmitch/nova,vmturbo/nova,mahak/nova,jianghuaw/nova,phenoxim/nova,CEG-FYP-OpenStack/scheduler,NeCTAR-RC/nova,openstack/nova,mikalstill/nova,zhimin711/nova,cernops/nova,Juniper/nova,cloudbase/nova,hanlind/nova,mahak/nova,dims/nova,rahulunair/nova,hanlind/nova,rahulunair/nova,cyx1231st/nova,BeyondTheClouds/nova,cloudbase/nova,rajalokan/nova,klmitch/nova,klmitch/nova,alaski/nova,bigswitch/nova,bigswitch/nova,cyx1231st/nova,zhimin711/nova,phenoxim/nova,sebrandon1/nova,mahak/nova,BeyondTheClouds/nova,BeyondTheClouds/nova,rajalokan/nova,openstack/nova,NeCTAR-RC/nova,hanlind/nova