install-guide: update some telemetry section titles

Some titles suggest that additional agents must be installed for glance,
cinder and swift to make ceilometer work. But those services just have
to be configured.

Change-Id: Iea05ee33ce9954142253f1c47e4709e57b305da7
autohelp: remove out of date doc in README.md

Provide a link to the openstack-doc-tools readme.

Change-Id: I05b3b08ac97c9820896ef3318fbf60522fd41b5e
Merge "install-guide: update some telemetry section titles"