updated code so that ET_Autocalibrate is only looking for fixations in half of the frame
* cleaned up the "convert" folder, which contains functions to convert ".mpg" to ".mp4" (in Windows, this must be done with the mmread toolbox as there is no support of .mpg)

* cleaned up the "prepare" folder

* added Work In Progress motion correction: the idea is to use the EPI motion parameters to correct the calibration model. It is not yet working satisfactorily, read the README.txt file for more info