Measurements documentation update
Measurements documentation update

Nova measurements:
- add cpu_util
- del disk.io.requests, disk.io.bytes
- add instance unit to instance:*

+fix some errors on type and unit

for all measurements add new column 'Origin' :
notification|pollster|both

tag : DocImpact
Fixes: bug #1164032

Change-Id: I0046032b8835168772fc7fff6c34a9be99ddbd56

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