Validation of most important cases for format in input file

1. Validation for cases when user entered not a number when needed
2. UnitTest correction (артем показывал)
3. Validation for cases when user entered group which doesn't exits in sheet 'Groups Info'
4. Validation for cases when user entered all 'no' in teacher preferences sheet
5. Validation for cases when user entered wrong name of sheet in input file
6. Validation when user enters not 'Yes' or not 'No' when entering sport electives reservation
7. Validation when user enters not 'Offline' or not 'Online' or not '-' when entering format of course
8. Validation when user enters not 'Full' or not 'Block 1' or not 'Block 2' when entering course type
9. Validation when user didn't entered preference for some of lecture teacher