URL-encoding forward-slash despite collection groups using this

[ak19]

cgiutils.cpp url-encodes several special chars, but its url-encoding of the forward slash has been temporarily disabled because of the forward slash being used in the qualified-collection names of collection groups, which broken when the forward slash was url-encoded.

We'd like cgiutils.cpp to still encode it, but for collection groups to still work. The idea is that it should be decoded back to a forward slash at the earliest possible time for the collection subgroups to work. Maybe other chars encoded by cgiutils can be decoded at this point also, in order for things to be back to 'normal'.

[ak19]

Maybe setting GSDL_COLLECT_DIR is a different way of allowing the forward slash to be encoded, while having access to the unencoded collection name.