Generator: match what is allowed in CellML 2.0 with regards to MathML (WIP).
Generator: match what is allowed in CellML 2.0 with regards to MathML (WIP).

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