Various improvements to slaprunner and shell in a box

• Shellinabox no longer needs password (nginx provides password)
• Do not popup for password when no account is set, redirect to account creation page instead
• shell now have proper $HOME and uses a real bash
• (see individual commits for more details)

I am not sure ssh is still functional, it did not work in my environment, but this might be because of my re6st setup.