Add migration policy to upgrades devref
Add migration policy to upgrades devref

Added a set of schema and data migration policy rules to the `upgrades`
devref document to facilitate live upgrades.

Change-Id: I4e38a228b38927115bb13652966d45f250cc2af6

CEG-FYP-OpenStack/scheduler,rahulunair/nova,BeyondTheClouds/nova,gooddata/openstack-nova,devendermishrajio/nova,vmturbo/nova,Francis-Liu/animated-broccoli,vmturbo/nova,raildo/nova,phenoxim/nova,felixma/nova,BeyondTheClouds/nova,yosshy/nova,rahulunair/nova,Francis-Liu/animated-broccoli,JianyuWang/nova,cernops/nova,noironetworks/nova,JianyuWang/nova,openstack/nova,ted-gould/nova,cloudbase/nova,Juniper/nova,CCI-MOC/nova,apporc/nova,cloudbase/nova,cyx1231st/nova,edulramirez/nova,hanlind/nova,cyx1231st/nova,cernops/nova,Juniper/nova,hanlind/nova,mahak/nova,TwinkleChawla/nova,bigswitch/nova,mahak/nova,klmitch/nova,BeyondTheClouds/nova,hanlind/nova,CCI-MOC/nova,alaski/nova,gooddata/openstack-nova,ted-gould/nova,klmitch/nova,rajalokan/nova,openstack/nova,mahak/nova,sebrandon1/nova,Juniper/nova,dims/nova,zhimin711/nova,fnordahl/nova,edulramirez/nova,sebrandon1/nova,NeCTAR-RC/nova,phenoxim/nova,j-carpentier/nova,alaski/nova,fnordahl/nova,zhimin711/nova,vmturbo/nova,rajalokan/nova,gooddata/openstack-nova,cloudbase/nova,MountainWei/nova,scripnichenko/nova,bigswitch/nova,gooddata/openstack-nova,vmturbo/nova,yosshy/nova,jianghuaw/nova,jianghuaw/nova,rajalokan/nova,mikalstill/nova,devendermishrajio/nova,sebrandon1/nova,NeCTAR-RC/nova,openstack/nova,jianghuaw/nova,rajalokan/nova,scripnichenko/nova,rahulunair/nova,j-carpentier/nova,apporc/nova,mikalstill/nova,Juniper/nova,raildo/nova,MountainWei/nova,klmitch/nova,mikalstill/nova,TwinkleChawla/nova,jianghuaw/nova,klmitch/nova,felixma/nova,cernops/nova,noironetworks/nova,CEG-FYP-OpenStack/scheduler,dims/nova