Generator: added some documentation for an origin comment.
Generator: added some documentation for an origin comment.

cellml/libcellml,nickerso/libcellml,MichaelClerx/libcellml,cellml/libcellml,MichaelClerx/libcellml,nickerso/libcellml,MichaelClerx/libcellml,nickerso/libcellml,hsorby/libcellml,hsorby/libcellml,hsorby/libcellml,cellml/libcellml,nickerso/libcellml,hsorby/libcellml,cellml/libcellml