Add prefix "$" for command examples
Add prefix "$" for command examples

This commits adds "$" as a prefix for command examples and align with
4 whitespaces.

Change-Id: Ida5f00f95251c6725bb96023591f0c1816d03f24

openstack/monasca-api,sapcc/monasca-api,sapcc/monasca-api,stackforge/monasca-api,stackforge/monasca-api,openstack/monasca-api,stackforge/monasca-api,openstack/monasca-api,sapcc/monasca-api,stackforge/monasca-api