Support for SSH keys for managing servers

[gigabit101]

Using the manage server option via the Mod Manager does not allow for use of SSH keys.
Using a password is insecure and it not supported via some hosting providers when using sFTP.

[mrjester888]

Trying to setup my first server. Not having SSH Key support means I have to weaken the default configuration of not allowing password authentication. Ideally, this would use the current systems SSH Agent socket to pull the SSH Key from the SSH Agent instead of needing to link to a key directly.