Allow value lists/arrays as property values

We are developing a tagging application. Instances can be tagged with one or more values. Currently one has to apply workarounds, like concatenating strings, using blobs, or power-of-two integers and doing interpretation work on the application side to be able to save more than one value to a property. This introduces unnecessary complexities and conventions into the code and is not a very robust way of handling this.

Please add this capability to VDMS.

New operator semantics for the constraints block would be useful. One would need to be able to indicate that the given search value(s) should be contained in the list of values on the property or match exactly the entire list of values in the property.

For example, `"constraints": { "tag": [ "<=", [ "valueA" ] ] }` to match all properties with a value list that contain at least "valueA". Or `"constraints": { "tag": [ "==", ["valueA", "valueB" ] ] }` to match all properties that have exactly this value list.