SYNTHMAINT-59 Simple JSON eval function for the CMS using the ParametersMap::FromJSON function

Create a CMS page with : <?EvalJSON&t={"hello":"world"}&of=json&template=<@@>?>

When running this page, the field "hello" should contain "world".

Or : ?SERVICE=EvalJSON&t={"hello":"world"}&of=json should return :

{
hello: "world"
}