From variable to constants for directories (at least it runs)

Signed-off-by: emanuele <emanuele45@gmail.com>
direcories defined in index.php (so that Settings.php doesn't change and should be even easier the upgrade)

Signed-off-by: emanuele <emanuele45@gmail.com>
Merge pull request #137 from emanuele45/dir_to_const

Dir to const