Create extras for pypi install

This patch adds a new [extras] to setup.cfg.  This section contains
support for drivers and their dependency requirements.  This allows
a user to pip install cinder and optionally install a driver's
required pypi based library.

For example, if you wanted to install cinder and support the 3PAR
driver, you would use:

pip install cinder[hpe3par]

This installs all of the cinder requirements as well as the requirements
for the hpe3par driver.

The following drivers weren't added to the extras stanza
rbd: No rados library in pypi
drbd:  There is no drbdmanage pypi package
linstor: no python-linstor pypi package
storpool:  pypi package doesn't install in python3 env

Change-Id: I2200ce6f554df0c988eb39521ce4defd75998a85

lower-constraints.txt

@@ -163,3 +163,13 @@ warlock==1.3.0
 WebOb==1.7.1
 wrapt==1.10.11
 oslo.upgradecheck==0.1.0
+websocket-client==0.32.0
+storops==0.5.10
+pywbem==0.7.0
+python-3parclient==4.1.0
+krest==1.3.0
+infinisdk==103.0.1
+capacity==1.3.10
+info.dtypes.wwn==0.1.1
+info.dtypes.iqn==0.4.0
+purestorage==1.6.0

setup.cfg

@@ -96,3 +96,34 @@ input_file = cinder/locale/cinder.pot
 keywords = _ gettext ngettext l_ lazy_gettext
 mapping_file = babel.cfg
 output_file = cinder/locale/cinder.pot
+
+[extras]
+all =
+    websocket-client>=0.32.0 # LGPLv2+
+    pyOpenSSL>=17.5.0 # Apache-2.0
+    storops>=0.5.10 # Apache-2.0
+    pywbem>=0.7.0  #LGPLv2.1+
+    python-3parclient>=4.1.0  # Apache-2.0
+    krest>=1.3.0 # Apache-2.0
+    infinisdk>=103.0.1 # BSD-3
+    purestorage>=1.6.0 # BSD
+datacore =
+    websocket-client>=0.32.0 # LGPLv2+
+powermax =
+    pyOpenSSL>=17.5.0 # Apache-2.0
+vnx =
+    storops>=0.5.10 # Apache-2.0
+unity =
+    storops>=0.5.10 # Apache-2.0
+fujitsu =
+    pywbem>=0.7.0  #LGPLv2.1+
+hpe3par =
+    python-3parclient>=4.1.0  # Apache-2.0
+kaminario =
+    krest>=1.3.0 # Apache-2.0
+ds8k =
+    pyOpenSSL>=17.5.0 # Apache-2.0
+infinidat =
+    infinisdk>=103.0.1 # BSD-3
+pure =
+    purestorage>=1.6.0 # BSD