Ceph

Keyring files should be easier to modify and not require the cumbersome cauthtool for that. This should ease installation.

The format we discusses will use the ceph conf format and will look like that:

[mon.]
   key = ...
   auid = 0

[client.admin]
   key = ...
   auid = 0
   caps mds = "allow" 
   caps mon = ...
   caps osd = ...

We should continue support the keyring binary format.
Man page should be updated accordingly.