TODO:

Graphical User Interface:
- better time expressions 
- editor for editing templates
- drag&drop for attaching files to records


Server:
- file handling
- user privileges
- Properly login hash handling
- Paging for search results
- roles for participants



known issues:
- It is not possible to set empty value in the field that allready has a value (I think this should be done explicitly -> "clear this field")
- Class tree is not in alphabetical order
- It is possible to remove required value