Refactor uninstall-script generation

[vector-of-bool]

This aside change refactors and changes a few minor issues with the uninstall script:

1. The script did not handle a late-defined install-prefix, and entered an infinite loop in that case
2. The script handled DESTDIR strangely (?)
3. There were two different generators: for Windows and for Unix
4. Using .bat scripting at all is just fraught with peril and should be avoided, if at all possible

This change also removes the top-level generate_uninstall/ directory, as well as the two generator scripts, instead replacing it with a single GenerateUninstalle.cmaker module (which should also be portable between projects).

[rcsanchez97]

I'm a little sad that you didn't like my generator script written in batch 😞

Seriously, though, this is much nicer. Aside from a few minor tweaks/questions, it looks good to me.

[rcsanchez97]

I am assuming that the DEBUG messages were meant to be left in. I don't have a problem with them (I rather like the extra output), but I wanted to mention it in the event you intended to remove them and forgot.

[vector-of-bool]

Yes, they were useful while debugging and don't get in the way, so I just left them there.

[rcsanchez97]

Is this how a collision is prevented between the uninstall generated in this project and, for instance, the uninstall generated in the C++ driver when it includes the C driver directly?

[vector-of-bool]

Yes. This is mostly the same as what was done previously, but with the addition of the newer CMake feature PROJECT_IS_TOP_LEVEL, which was added to address this exact use case (on older CMake, that variable check will be a no-op).