give the "un-log" of predicted values for regression problems if relevant

[ClimbsRocks]

data-formatter is going to start taking the log of regression values in most cases.

when making final predictions, un-log the values

when making stage 0 predictions, modify the output column to say "log(OUTPUT_HEADER_NAME)", to make it clear to everyone that in order for these predictions to be useful, you must un-log them. otherwise, they're intended for ensembler to use