R/calculate_intensity.R: cleaned output of step 3 of the plotFeatures function

Signed-off-by: Charles Joly Beauparlant <Charles.Joly-Beauparlant@crchul.ulaval.ca>
R/calculate_intensity.R: added the step 4 -> Merge matrix

Signed-off-by: Charles Joly Beauparlant <Charles.Joly-Beauparlant@crchul.ulaval.ca>