Custom version for the user "math user".

1) The user can add a preferred time directly in the add activity dialog.
For the user "math user", on forum: http://lalescu.ro/liviu/fet/forum/index.php?topic=2502

2) The user can add with a single button constraints activities occupy max 1 different rooms
for all subactivities of an activity. This is done from the menu Advanced.

3) The user can add a preferred room for activities in the add activity dialog.

4) The CSS file for the output timetables is a bit customized.