man/plotFeatures.Rd: Added the manual page for the function plotFeatures

Signed-off-by: Charles Joly Beauparlant <Charles.Joly-Beauparlant@crchul.ulaval.ca>
DESCRIPTION: minor corrections in Description field

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