Adding feature to create an volume from an snapshot.

Signed-off-by: Udara Liyanage <udara@wso2.com>
removing subscribeToCartridge method

StratosAdmin Subscribe() calls SubscribeToCartridge which calls subscribe with same parameters. So subscribeToCartidge() is not needed.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-stratos