Appearence changes
Added 'AddGroup' and 'RemoveGroup' for class 'ClassesTable'.
Bugfix in Alex code: when generated titels, now ignored groups without specialization.
Merge pull request #10 from ladagagina/master

Import to Excel
Merge pull request #11 from Lozov-Petr/model

Add: group adding and removing
Add: inplace group and specialization renaming
Add: adding and removing group in table
Add: import menu (import doesn't work)
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..
Restore after git crash (!?)
Merge branch 'gui'
Not save empty classcard
Remove Enter as edit command
Add Group and ClassTime to ClassRecord
Reorganize classes
Create abstract ClassesTable class with type parameter
..
Create abstract ClassesTable and its child GroupClasses
Serialize without ClassesTables.