doc: how to inject user-defined data
doc: how to inject user-defined data

Change-Id: Ieb7e391cd27a60035faa075e5944bc36424992c7

idegtiarov/ceilometer,pkilambi/ceilometer,citrix-openstack-build/ceilometer,cernops/ceilometer,tanglei528/ceilometer,froyobin/ceilometer,ityaptin/ceilometer,luogangyi/Ceilometer-oVirt,maestro-hybrid-cloud/ceilometer,pczerkas/aodh,rackerlabs/instrumented-ceilometer,isyippee/ceilometer,JioCloud/ceilometer,sileht/aodh,citrix-openstack-build/ceilometer,sileht/aodh,rackerlabs/instrumented-ceilometer,rickerc/ceilometer_audit,redhat-openstack/ceilometer,mathslinux/ceilometer,isyippee/ceilometer,fabian4/ceilometer,cernops/ceilometer,openstack/ceilometer,idegtiarov/ceilometer,openstack/aodh,m1093782566/openstack_org_ceilometer,r-mibu/ceilometer,pkilambi/ceilometer,pczerkas/aodh,chungg/aodh,MisterPup/Ceilometer-Juno-Extension,tanglei528/ceilometer,Juniper/ceilometer,Juniper/ceilometer,fabian4/ceilometer,luogangyi/Ceilometer-oVirt,openstack/aodh,JioCloud/ceilometer,rackerlabs/instrumented-ceilometer,r-mibu/ceilometer,openstack/ceilometer,froyobin/ceilometer,mathslinux/ceilometer,rickerc/ceilometer_audit,tanglei528/ceilometer,m1093782566/openstack_org_ceilometer,eayunstack/ceilometer,redhat-openstack/ceilometer,maestro-hybrid-cloud/ceilometer,rickerc/ceilometer_audit,NeCTAR-RC/ceilometer,ityaptin/ceilometer,JioCloud/ceilometer,eayunstack/ceilometer,chungg/aodh,citrix-openstack-build/ceilometer,NeCTAR-RC/ceilometer,MisterPup/Ceilometer-Juno-Extension,NeCTAR-RC/ceilometer