Implemented the "filter first" for the following identity panels:
- Users
- Groups
- Roles
- Projects
The functionality helps horizon not to hang and timeout when there is
a large set of identity resources to display. It can be turned on and
off easily.
In a subsequent patch set the same functionality will be added to
other identity views such as Project > Manage Members
Change-Id: I6e569712fb5159552a27271837cf2629059f5894
33fcd95caf