[minor] Added how to setup COAL for image management
[minor] Added how to setup COAL for image management

arekinath/sdc-cloudapi,arekinath/sdc-cloudapi,misterbisson/sdc-cloudapi,KrisShannon/sdc-cloudapi,KrisShannon/sdc-cloudapi,joyent/sdc-cloudapi,misterbisson/sdc-cloudapi,joyent/sdc-cloudapi