If no htpasswd file exist, redirect to account creation page

This should not depend on the environment when executing slapos node
instance

Since shellinabox listen on AF_UNIX, we don't need another password for
shellinabox

Interesting new features:
 * unix domain support
 * copy & paste with browser integration (Ctrl+C, Paste from browser in
 * popup)
 * warn before closing
 * fix bug when zooming from browser

For compatibility, the new shellinabox is named 'shellinabox-github'.
The previous component with ipv6 support is kept as 'shellinabox-2.10'
and is still the default when using 'shellinabox'

Section "KVM instance (1GB of RAM, 10GB of SSD, one core)" was put there
twice with exactly the same text.

Remove duplicate.

/reviewed-by TrustMe
/cc @alain.takoudjou

 Those signatures are old and unused anymore.