public String getDefaultFont() {
// First look at the defaults
// 3 look at styles/rPrDefault
// eg
// 3.1 if there is an rFonts element, do what it says (it may refer you to the theme part,
// in which case if there is no theme part, default to "internally stored settings"
// (there is no normal.dot; see http://support.microsoft.com/kb/924460/en-us )
// in this case Calibri and Cambria)
// 3.2 if there is no rFonts element, default to Times New Roman.