Iscsi Manager and CLI iSCCI Module

New iSCSI manager has been introduced to conveniently work with iSCSI
service provided by SofyLayer. Respective CLI module has also been
introduced for CLI interaction.
Incorporated suggested changes

corrected command listing style and divided iSCSI section and snapshot section.
Modified filter for ISCSI and snapshot Item price IDs
Improved the docopt docs with example, etc.
Using custom response inside tests

Fixure Product_Package has too many things which are not required by the iscsi tests. Using return_value from `mock` to test iscsi manager.
Merge branch 'master' into iscsi-manager
Merge pull request #302 from aparnapatil/iscsi-manager

Improves iscsi manager