Minimalistic CMake port

[JayFoxRox]

I actually expect this to be rejected - this is mostly here for exposure, for people like me, who have issues with autogen. This CMake build system is very incomplete, but made it much easier to compile concordance for me.

[jaymzh]

./configure; make; sudo make install is pretty straight forward.

[JayFoxRox]

./configure; make; sudo make install is pretty straight forward.

Except it's not that easy:

• libconcord also depends on libusb/hidapi and libzip. It did not find those which I had installed via brew on macOS. I can't be bothered to fetch X dependencies and compile them all by hand (or to look for them on the filesystem, which is a bit messy on macOS).
• Installing system wide is not an option on this system, the uninstall steps also looked too complicated, so even if I was okay with full system access I'd not do it.
• In general, it would not be managed by the package manager so I'd be concerned about potential breakage in the future (when deps are modified); I'd also not be reminded about it when it comes to system cleanup / maintenance.
• I wanted multiple out-of-tree builds so I could skip USB access while faking communication to the website (while having another version which still does all the work). I wanted to avoid having to set up the dynamic linker / static linker to avoid any problems (and I trust CMake out-of-tree builds in this regard).
• I've never liked the GNU build system because of a handful issues which can quickly do unintended things (spaces in filenames, wildcards doing stupid things, ..). CMake is at least slightly more sane in this regard.

Altogether it took me less time to make the CMake port than it would have taken to make ./configure work properly (which I tried). Part of it might have been that I stopped using the GNU build system almost 15 years ago (and don't plan to go back to it). I'm much more familiar with CMake by now and that has also gotten more widespread industry support by IDEs, package-managers etc.