For this we need to enhance a lot of stuff:
- Create (optional) logicOps collections within the ogcFilter
- If one ore more logicOps are defined, disable the option to add individual field-value pairs unless you define an existing logicOp
- If a field-value-sign is defined, disable the possibility to add logicOps
- Create the option to nest logicOps inside logicOps
For more information on logicOps see: http://schemas.opengis.net/filter/1.1.0/filter.xsd