Ignore categories in vislay

[ischas]

Since categories are defined as always visible, they appear in vislays. This leads to unnecessarily long URLs.

[ischas]

Moreover, you have to add each category of active layers to the vislay-parameter to show the layer.

[ischas]

Moreover, no other layers are selectable anymore when using vislay-parameter without mentioning the corresponding categotry in vislay categories.