Only allow SSH for itadmin group
Create home directories as 0700

A vulnerability existed where another user could read files in a home area due
to permissive access of 0755.
Add flags to disable updating scripts or configuration

The following flags have been added:
 * no_update_scripts - Do not update scripts
 * no_update_config - Do not update configuration
 * no_update_skel - Do not update skel
 * no_update_other - Do not update non-essential configuration
 * no_update_icons - Do not update desktop icons
 * no_update_printers - Do not update printers

These can be set with `karoshi-manage-flags set <flag>` and unset with
`karoshi-manage-flags unset <flag>`, however they will not show up in the GUI