moved "hideallitems" tag from advancedsettings.xml to GUISettings

This is one of the things that I always wondered why it is not integrated in the GUI.
Hiding the all items entry is one of the first things I do when installing a new XBMC.
Also I saw several threads in the forum where users asked for this feature and did not know about the possibility to handle this via as.xml

Basically this was some coding excercise for me. Maybe your interested. Any comments?
Any whitespace grinches?

cheers,
mad-max