Exporting .fet file of a single (selected) day

[Vangelis Karafillidis]

Sometimes, the user needs to modify the timetable of a single day because a couple of teachers are absent. It would be really useful, if the user could export a new .fet file (from the generated timetable) for a selected day. For example, if the user needs to modify his timetable for Monday, because two teachers are absent, he could extract a new .fet file with
days = 1
teachers the same as the original file
students the same as the original file
and activities the activities of this specific day.
Most of the time constraints should be removed, but some constraints such as teacher not available times, teacher max hour continuously, teacher max gaps per day, etc could be selected by the user in order to be extracted to the new (generated) .fet file. Then the user could add some constraints in order to avoid the gaps for the students groups, and generate a new timetable.
Vangelis.

[Liviu Lalescu]

Added in the TODO. Unfortunately, too complicated for me for now.