Improved manual fixation selection

Displaying fixations automatically detected in the spatial and temporal
domains. User then selects fixations in the order that they are
displayed in the gaze axes. If some fixations are missing, user hits
'return' key without selecting any point on the heat map display.
Added validation video analysis

if no validation video present, it's fine. If it is there, then it is
analyzed and the model is estimated from validation fixations as well.
VideoUtils was crashing on Windows

Added ismac switch where necessary. If ispc, use Matlab builtin
VideoReader/VideoWriter.
Updated MR Clean

The thresholding for type 1 and type 2 artifacts was not working
optimally. As a quick fix, always correct as if positive artifact, since
these is the most detrimental ones for pupil segmentation.
ROI remains fixed after calibration

no re-centering of the ROI from the gaze video poster frame. This could
be problematic if there is gross motion between calibration and gaze
videos. We can use a larger ROI if this becomes a problem.
Update to glint detection

the assumption that "height is correct, width is overestimated" is not
general. Implemented an agnostic version, which may need further
improvement.
Visual Alignment check in the html report