doc: Add ECDSA keys to docs, make key docs consistent
doc: Add ECDSA keys to docs, make key docs consistent

Signed-off-by: Alan Dunn <90d3ad16cd4565f91305ac667132a38a0361079b@gmail.com>
Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>
(cherry picked from commit f6276fe73940dd35bbd4f95d3cf902bcf69f23f3)

mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/ssh,mwgoldsmith/libssh,mwgoldsmith/libssh,mwgoldsmith/ssh,mwgoldsmith/libssh