Tee output from tesseract into log file

[ElectricRCAircraftGuy]

It would be useful to store tesseract's output in a log file named "mypdf_searchable.log", in order to review messages later. So, add this feature.

Note that this keeps 1 output log file per output searchable pdf, which is the desired behavior, so that log messages generated for a given pdf which was created are easily reviewed.