Improve help text for quota options
Improve help text for quota options

This commit adds additional help text to the quota
config options from "nova/conf/quota.py"

Change-Id: I7e1986c5f11356060cc9db12605b1322c39e79c0
Implements: blueprint centralize-config-options-newton

klmitch/nova,mahak/nova,jianghuaw/nova,openstack/nova,hanlind/nova,sebrandon1/nova,rahulunair/nova,vmturbo/nova,vmturbo/nova,klmitch/nova,gooddata/openstack-nova,gooddata/openstack-nova,mikalstill/nova,rajalokan/nova,gooddata/openstack-nova,cloudbase/nova,hanlind/nova,openstack/nova,mikalstill/nova,hanlind/nova,alaski/nova,jianghuaw/nova,mahak/nova,klmitch/nova,rahulunair/nova,alaski/nova,openstack/nova,vmturbo/nova,cloudbase/nova,sebrandon1/nova,jianghuaw/nova,mahak/nova,Juniper/nova,phenoxim/nova,gooddata/openstack-nova,rajalokan/nova,rajalokan/nova,Juniper/nova,rajalokan/nova,vmturbo/nova,sebrandon1/nova,cloudbase/nova,mikalstill/nova,rahulunair/nova,Juniper/nova,jianghuaw/nova,phenoxim/nova,klmitch/nova,Juniper/nova