Change the default non-set values to null if the mendatory fields are set to optional via the settings.php file

# Conflicts:
#	backend/Pianos4.php

# Conflicts:
#	backend/TE/TakeExercise.php
#	js/pianos4_view.js

# Conflicts:
#	js/pianos4.js

Set the mark size and size-factor as global variable, and first test to the normalized length for the minutiae annotation compatible with AFIS annotation system