Gets and sets the source spatial reference wkt to be used to select the SourceSpatialReference for the
TransformationInfo object (used to populate a table row).
The SourceWkt is optional. The default is null. The SourceVcsWkt should also be defined if a vertical coordinate system needs to be selected. If the SourceWkt (and the SourceVcsWkt if applicable) is set, then the corresponding SourceSpatialReference with that wkt (and vcsWkt) will be selected for the TransformationInfo object. Note: only one of: o SourceSpatialReference o SourceWkid, and SourceVcsWkid if applicable o SourceWkt, and SourceVcsWkt if applicable need be set. If the SourceSpatialReference is set, Wkids and Wkts are ignored. If the SourceSpatialReference is null, then Wkids are used. If the Wkids are 0 (or less), then the Wkts are used.