Major reimplementation of the handling of student data.

- Students can be identified by name/surname or simply by full name.
- Dialog for creating new students from the student selection dialog.
Add test cases for reading student lists from file.
Update the user manual for the new student management.

- Student id list file format.
- Dialog for creating new students.
Update the export tool to the new student management.
Merge branch 'students2' into development.