Adding python-saharaclient to requirements

The python-saharaclient is necessary for the Sahara
dashboard to interact with the Sahara-api service, so it is being
added to requirements.txt.

Change-Id: Ia3374a6792a4b0d2388f3826e88d92136a2b5e63
Partial-Implements:  blueprint merge-sahara-dashboard
Updated from global requirements

Change-Id: Iba7e7b0c64af522174ec149736c824de7227d0ee
Use the domain filter provided by keystoneclient

The keystone api client in horizon has it's own filter
by domain implementation for group listing. Switch
this over to use the keystoneclient domain filter for
a cleaner implementation.

Change-Id: Ie47b27ddc8bcaa9b9f22c5925580b8889a65c1d0
Closes-Bug: #1306213
Merge "Adding python-saharaclient to requirements"
Merge "Use the domain filter provided by keystoneclient"