updated DataDefs to have helpful comments
updated DataDefs to have helpful comments

JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software,JacquesCarette/literate-scientific-software