roslaunch option to log to both: screen and logfile

Replaces PR #413

For output = both
-> stdout will be written to screen and logfileout
-> stderr will be redirected to stdout, this will keep temporal order between out and err intact on screen and log file, but err messages will be written with out messages to logfileout.
-> no stderr log file

For output = log
-> stdout will be written to logfileout
-> stderr will be written to screen and logfileerr
-> temporal order not intact, but doesn't matter because files are separated and only err messages are shown on screen

For output = screen
-> stays as is, no multiplexing is needed