OpenSSH server using environment variables

this is initial implementation that works, but some design changes will most probably be needed to avoid copy&paste from openssh backend (at least the definition of the ciphers should be the same).

Let me know about your opinion about this and I can fix/improve that.

Edit: Fixed testsuite. Should be ready for https://fedoraproject.org/wiki/Changes/OpenSSH_Server_Crypto_Policy