Add Support for Dell Storage Center

This driver implements cinder FC and iSCSI volume drivers.
The file dell_storagecenter_api.py is called to interface with the
Dell Storage Center backend via a REST interface.
Dell_storagecenter_common.py is the base class implementation with
dell_storagecenter_fc.py and dell_storagecenter_iscsi.py being providing
fc and iscsi specific support respectivly.

https://bugs.launchpad.net/cinder/+bug/1398951

Implements: blueprint dell-storage-center-block-storage-driver
Change-Id: Ic483e54b40349ede20e078c6406f5bab8d7d7cc2
Merge "Add Support for Dell Storage Center"