Support properties from other classes in Live Data

In LiveTable, it is possible to specify properties from XClasses different from the "main" XClass by adding an extra parameter:

This option can also be used to view properties of classes other than the one declared in className ("extraParams" : "&yourProperty_class=yourSpace.yourClass" - sorting and filtering available from version 6.2.1.)

Live Data kind of supports the same feature by directly specifying yourProperty_class=yourSpace.yourClass in the source parameters. However, currently, no metadata for the property is loaded in this case which makes it much less usable. This should be improved by loading the metadata from the specified class.