Empty multi-value String properties get bootstrapped as type Double

It appears that we use Node#setProperty(String name, Value[] values) when creating an empty multi-valued property. There is not way to convey the desired type in this API, and apparently, Jackrabbit defaults to Double.

Instead, we may need to use the Node#setProperty(String name, Value[] values, int type) API to make sure the correct type is used (typically: String).