Option for Rcaller print statements to translation log

I would like to see the log of R in the transition log because;

- Sometimes functions in R can take a long time. For some functions you are able to keep track on its progress by Verbose=T.
- For debugging, it is useful to use print statements for intermediate results
- At this point, custom transformers using Rcallers are a black box to other users. Exposing intermediate results can prevent this.

Now the print statements only occur if an error is found.