Update to 5.25.0:

Version 5.24.0
- Version 5.24.0
	- Updated to Qt 5.4.0.
	- Significant speed improvements when using many students sets (suggested by Volker Dirr).
	- Speed improvements in the statistics menu.
	- Other speed improvements for larger data.
	- Added an option to hide students subgroups in combo boxes/activity planning (useful if you have too many students subgroups
	and you don't use them in the interface).
	- Added options to select the categories of timetables to write on the hard disk.
	- Automatic division of years by categories is improved (suggested by alxgudea, Bobby Wise and Volker Dirr).
	- Code improvement in reading the .fet XML files: converted from the obsolete Qt classes QDom* to QXmlStreamReader. It brings
	speed and memory improvements when reading the input files, and ensures FET source compatibility with future Qt versions.
	Also error reporting when reading a corrupt file is improved. The structure of the .fet XML files is slightly changed,
	but of course older files are opened correctly.
	- Several bug fixes, when trying to open corrupt files.
	- Other bug fixes, reported by Vanyo Georgiev.
	- It is now allowed to have constraints preferred/home rooms with a single room (suggested by liquid and Volker Dirr).
	- Added a new example file from Vietnam, by nguyenhuuduyet.
	- Added a new example file from Namibia, by Bobby Wise.
	- Added two anonymous example files.
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Versions 5.25.0 - 5.25.x
- Version 5.25.0
	- Improved the split year dialog: groups and subgroups which will exist in this year after the division will retain their activities and constraints.
	- Sort (temporarily) the constraints by description in the all time/space constraints dialogs. Also, removed the 'Sort by comments' button,
	which is probably useless.
	- Fixed a bug introduced in version 5.24.0: when having individually modified activities, removing teachers, subjects, activity tags,
	or students sets could remove only some components of the large split activity.
	- Some minor strings improvements.


(wiz)