Instructions on image creation for SoftwareConfig.

Instructions on creating images that can be used for SoftwareConfig and
SoftwareDeployment are added.

Change-Id: If4bc6197ca38d73378ada6a6b32e47a658d88fc5
Make some properties updatable for Volume resource

Make 'name', 'description' and 'metadata' updatable for
OS::Cinder::Volume resource.

Change-Id: I2783b689470ccbff0deab01df3df61e36e1a54d6
Closes-bug: #1330886
Merge "Instructions on image creation for SoftwareConfig."
Merge "Make some properties updatable for Volume resource"