[MERGE][bug #183705] Update authentication docs regarding ssh agents.

[Vincent Ladeuil]

>>>>> "john" == John Arbash Meinel <john at arbash-meinel.com> writes:

<snip/>

    john> I believe these statements aren't strictly true without
    john> your other patch.

More or less. But at least now the doc doesn't recommend setup
that will not work. If some setups work even if the doc say they
shouldn't, I'm less worried.

    john> Since we allow ssh passwords some-of-the-time
    john> (paramiko).

This is a grey area... I still need to write some tests to better
understand what is and what is not possible here, I wonder if we
should continue let users transmit password through bzr that way
or not.

       Vincent