Clarify description of hierarchical component cleaning
Clarify description of hierarchical component cleaning

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