Used to be: 1,2,5-10 (ranges inclusive)
Now: 1,2,5:11:1 (like python lists)
Now 'to' number is not-inclusive; dash replaced with colon (to support
negatives); added support for missing values; added support of step
Now, when executing a newly created feature fails, an error message is
displayed. Moreover, messages are going to be displayed where only
warnings were dumped to console, previously.
Unhide originals when deleting features that hide originals.
Special logic with explode (prevent unhiding), to be able to delete
unneeded stuff easily.
Strangely, but when outputting the child directly when only one shape
makes it through the filter, its placement is totally messed up, so it
causes viewer errors. That's funny.
