Add to interface ability to set content search sensitivity

[maximka1812]

CLI version has

--content-detection=<cautious|normal|aggressive> -- default: normal

I don't see it anywhere in interface. Adding it to left panel can be very helpful as ST frequently likes to miss headers or page numbers.
or instead can decide that shaded page turn also belong to content.

[trufanov-nok]

This in fact is a Despeckle level. I don't know why it's called "content-detection". This is inherited from the original project: https://github.com/scantailor/scantailor/blob/master/CommandLine.cpp#L363
You're the second guy who actually tried to work with a *-cli version of this fork. So if you think this is misleading - i can change it.

[maximka1812]

You can change text as you'll have some time for this. I am more interested to be able to adjust ST behavior with small items that it so much like to miss.

Is it very hard to port ST Advanced feature were it extend content area upon click outside it?

Btw, even simple extension of content area so it'll include click coordinate is also big time saves as dragging the border requires much more time and precise aim.