Allow a target of "not worse"

[dennis-sig]

Requested/proposed by a client to @SebGondron. This type of suggestion fits well with our boy scout rule storyline, and it's a very pragmatic solution for systems that are very large and/or old and/or use older technologies.

[JohanVT]

We are currently switching from FTP upload to SigridCI for several scientific/computational/modeling applications, using a mix of technologies (Fortran, C#, Python, Ruby, and more) within the same project.

I decided to set the targetquality to 0 because the results of other values feel too random.
The "not worse" target would be very helpful!

Assuming "not worse" is determined for existing code by comparing the results of the same sources. For new source files it's probably best to keep using the targetquality?

[MichielCuijpers]

thanks @JohanVT