[-] Core : Fixed robots.txt Disallow

Actual code is too generic and blocks too much urls

i.e.
"/*n="   matches also the URL "/something?isit=a&pain=yes" .. and it is wrong

As we think the controller=controller_name is quite safe the proposed patch acts only on generic parameters not having a value .. in order to have a smaller robots.txt (not specifying controllers too twice)
Merge pull request #2244 from ZiZuu-store/patch-1

[-] Core : Fixed robots.txt Disallow