Root resource behavior (/sign-up)

Set up root resource handling as follows:

account creation	logged in as	behavior
disabled	n/a	show login
disabled	normal user	show logout
disabled	admin	show logout
admin	n/a	show login
admin	normal user	show logout
admin	admin	sign-up
public	n/a	sign-up
public	normal user	show logout
public	admin	sign-up