Internal function checking and loading dFs or sPDFs to
mapCountryData, mapPolys, mapPies,
mapBubbles, mapBars.
rwmCheckAndLoadInput(inputData = "", inputNeeded = "sPDF",
callingFunction = "")invisibly returns a dF or sPDF
a dF, sPDF or "", for latter an internal example data is used
"sPDF", "sPDF or dF", "dF"
optional : name of the calling function
andy south
a rworldmap internal function, unlikely to be of use to users