bring spatial features in and out of the RCaller

It would be nice if we could bring geometry directly into the RCaller, so that we may manipulate that geometry with our R code. Currently, we have to write a temporary file and read that temporary geometry file in the RCaller. It would be nice if R could recognize incoming geometry and build that geometry in the R spatial data model. Then we can manipulate the geometry in R code, and output the manipulated geometry back to our FME workspace.