easy option to use canvasmath (MathML) or MathQuill (LaTeX) to render FormulaText, FractionText, ContinuedFraction + tidying

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23921 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e