Add driver dependencies as extras

Adds Cinder Driver's Python dependencies as setuptools extras to
facilitate their dependency control.

The libraries and version have been extracted from the
driver-requirements.txt file in Cinder's Pike branch.

setup.py

@@ -17,6 +17,36 @@ test_requirements = [
     # TODO: put package test requirements here
 ]
 
+extras = {
+    # DRBD
+    'drbd': ['dbus', 'drbdmanage'],
+    # HPE 3PAR
+    '3par': ['hpe3parclient>=4.1.0'],
+    # Kaminario
+    'kaminario': ['krest>=1.3.0'],
+    # Pure
+    'pure': ['purestorage>=1.6.0'],
+    # Dell EMC VMAX
+    'vmax': ['pyOpenSSL>=1.0.0'],
+    # IBM DS8K
+    'ds8k': ['pyOpenSSL>=1.0.0'],
+    # HPE Lefthand
+    'lefthand': ['python-lefthandclient>=2.0.0'],
+    # Fujitsu Eternus DX
+    'eternus': ['pywbem>=0.7.0'],
+    # IBM XIV
+    'xiv': ['pyxcli>=1.1.5'],
+    # RBD/Ceph
+    'rbd': ['rados', 'rbd'],
+    # Dell EMC VNX
+    'vnx': ['storops>=0.4.8'],
+    # Violin
+    'violin': ['vmemclient>=1.1.8'],
+    # INFINIDAT
+    'infinidat': ['infinisdk', 'capacity', 'infi.dtypes.wwn',
+                  'infi.dtypes.iqn'],
+}
+
 setup(
     name='cinderlib',
     version='0.1.0',
@@ -33,6 +63,7 @@ setup(
                  'cinderlib'},
     include_package_data=True,
     install_requires=requirements,
+    extras_requires=extras,
     license="Apache Software License 2.0",
     zip_safe=False,
     keywords='cinderlib',
@@ -49,5 +80,5 @@ setup(
         'Programming Language :: Python :: 3.5',
     ],
     test_suite='tests',
-    tests_require=test_requirements
+    tests_require=test_requirements,
 )