Possibility to export a casebase as csv file

Lotta Rintala asked for the posibility to be able to save a case base seperately in a csv file.

Workflow for exporting a case base as csv file:

1. Adding "Case Base" main menu item
2. Add entry "Export"
3. Open dialog
4. Select case base to be exported and location to save
5. Click okay to save the csv (also add an option to cancel here)