Included a function to start model-free calculation from log windows and control it.
This corresponds to the include_modelfree_logwindow_patch file attached to https://gna.org/task/?6847 by
Michael Bieri (https://gna.org/users/michaelbieri), in the zip file 100121_patches.tar.gz
(https://gna.org/support/download.php?file_id=7726).
This commit should have been in 2 patches - it includes a '/' to os.sep fix as well!
