5.1.1 update to authorization feature

Document updates to Fuel Authorization being implemented in 5.1.1.
This is similar to 6.0 implementation, but the following changes
are not implemented in 5.1.1:
- keystonemiddleware
- Nailgun and OSTF services endpoints in Keystone
- nailgun and ostf users in services project
- authentication token that does not expire for 24 hours

operations: update 6500-fuel-auth with info about new features

user-guide:
- Add --password option for fuel CLI
- 8000-upgrade is xref'ed from this commit but the instructions
  to supply the password are NOT in this commit; they are in the
  upgrade commit for smoother reviewing.

terminology/Keystone -- an instance of Keystone runs in a container now
in addition to the instances that run on the target nodes.

Change-Id: I355afa66f12deee46f6c05337d137d1703227134
Partial-Bug: 1384343
Partial-Bug: 1387667
Partial-Bug: 1392626
Closes-Bug: 1392289