Updated Excel export filenames and tooltip info texts

Excel exports

• The filename format is now more consistent: the format for most filenames is oodikone_featureName_date.xlsx, for example: oodikone_students_2024-01-11.xlsx

Completed courses, study programme overview

• Updated info texts

Course stats

• Removed unnecessary filtering that led to some students not showing in the grade distribution table

Internal

• Removed unnecessary dependencies
• Moved some files into more logical folders