DimensionUsage is usage of a shared dimension within the context of a
|Name of the source dimension. Must be a dimension in this schema. Case-sensitive.
|Name of the level to join to. If not specified, joins to the lowest level of the dimension.
|If present, then this is prepended to the Dimension column names during the building of collapse dimension aggregates allowing 1) different dimension usages to be disambiguated during aggregate table recognition and 2) multiple shared dimensions that have common column names to be disambiguated.