* Rename polylinefilter to polygonfilter
* Update icon name, too
* Some GUI adjustments
* Remove obsolete code that came back in a merge somewhere.
Disable auto-enable polygon filter after picking corner points.
* Add option to delete a point in polygon filter point editor by extending generic picker interface
* Rename enum, too.
* Improved filter naming
Co-authored-by: Magne Sjaastad <magne.sjaastad@ceetronsolutions.com>