Statistics on personal notes by free-text filters

Boltenheide wants to count entries that refer to so-alled "Lob- und Regelverstoßeinträge". They are entered as L1, L2, L3, R1, R2 or R3.

The generalisation of this is that we allow defining filters, e.g. regular expressions, that are then evaluated and counted when generating reports.

• Define data model for the filter definitions
• Create UI for managing (add, delete, edit) filter definitions