Provide validation and settings to KLE fields.

- Validation to only use existing terms
- Validation to only use terms starting with xx.xx.xx
- Settings to set KLE non-required and hidden. These are set in ``admin/config/os2web/settings``
Add button to delete all refs from a certain content type.
Merge pull request #2 from syddjurs/feature/SYDDK-126_SYDDK-127_KLE

Provide validation and settings to KLE fields on all content types.