Add SSH access level to TD

Currently the phase for (optional) setting up the SSH access is missing, which may affect metrics used for computing next levels.

The root account at the attacker machine can't be now accessed via SSH. The user has to connect to the default account (user-access) using a command like ssh -F pool-id-1-sandbox-id-1-user-config attacker and then use su root. Add these commands and notes to the SSH access level.