[crypto] Encode unicode strings in _cypherer() pycrypto accept both bytes or string but pycryptodome, which will be introduced in next changeset, doesn't accept this. For backward compatibility, encode unicode strings in _cypherer()

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances