remove insecure ssh options

The current code runs ssh with CheckHostIP=no and StrictHostKeyChecking=no
on the command line. These are security-sensitive options which an
application should not change without the user's knowledge. Setting
hostkey checking this way is particularly bad, since in this mode
Macfusion will silently connect to a spoofed server a user has
specifically verified in the past (ssh issues a warning, but Macfusion
ignores it and does not present it to the user).

I have removed the options; a user can add them in ~/.ssh/config or in the
Macfusion "SSH Advanced" tab if he actually wants them.
Do not output the password in DebugMode unless
specifically told so with NSDebugEnabled. Too much
of a problem, when it stays there in logs.