Remove references to IBM AFS

Remove references to IBM AFS

Change references to the documentation sets that we still ship to
reference the OpenAFS manuals instead of the IBM AFS manuals.  Remove
references to the IBM AFS/DFS Migration documentation, since that
doesn't appear to be available anywhere any more, replacing them where
relevant to more generic references to the DFS documentation.  Add
links to docs.openafs.org for mentions of the manuals in SEE ALSO, and
standardize on one link format.  Replace a few references to the IBM
AFS Release Notes with the actual information in those notes, or drop
the reference if it doesn't seem particularly useful.

Change-Id: Ie9666842f1315891c6a9c37c0424200f4b78bff7
Reviewed-on: http://gerrit.openafs.org/2031
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>