* Support case insensitive matching in prefix/suffix operators
Support `caseinsensitive`/`caseinsensitive` suffixes in the following
filter operators:
* prefix
* suffix
* removeprefix
* removesuffix
The suffixes have the same behaviour as in the match operator.
Closes: #6407
* Do not filter titles if suffix/removesuffix operand is empty
Issue: #6407
Now the $:/ part of the name is rendered in grey, making the main part
of the title more prominent.
@tobibeer suggested this a long time ago; good idea!