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: I974715879db5d60494fb2bd0b2fd247570a1e623

openstack/monasca-common,openstack/monasca-common,stackforge/monasca-common,stackforge/monasca-common,openstack/monasca-common,stackforge/monasca-common