respect a custom ID separator when decomposing a list of IDs as well as a single ID
Fix bugs with multi-part IDs and in-clauses.

In some cases a multi-part ID in a boolean expression, when normalized,
would begin to believe it was "unique" (specifying only one object),
even if the expression used an ambigous clasue (in-clause, like, etc.)
Updated loading for UR::Value subclasses with multi-part IDs.

Previously, a multi-part ID subclass of UR::Value would not load
correctly when an in-clause was passed-in.  This is now fixed.