Change: rebrand 1.12.0 to 12.0

One question that keeps popping up: "when do we release 2.0?".
NewGRF will force that at least 1.16 will be 2.0, but to not wait
for this, let's drop the "1." and be for ever done with that
conversation.

We are following in the footstep of giants here.

Fix: [CMake] if the regex for STABLETAG is empty, it means it is stable

This feels a bit inside out, but it makes sense: if there are no
"beta1" or "RC1" mentions, it means it is a stable release.

Fix: fix building release tags

I tried building a tag, and got this error:

CMake Error at cmake/scripts/FindVersion.cmake:85 (string):
string sub-command REGEX, mode REPLACE: regex "^[0-9.]*$" matched an empty
string.

Fix: [AzurePipelines] switch the CI / CD to CMake too

This also means dropping Debian/jessie, as it has a CMake that is
too old (3.0), with no real path to upgrade.

Add: introduce CMake for project management

CMake works on all our supported platforms, like MSVC, Mingw, GCC,
Clang, and many more. It allows for a single way of doing things,
so no longer we need shell scripts and vbs scripts to work on all
our supported platforms.

Additionally, CMake allows to generate project files for like MSVC,
KDevelop, etc.

This heavily reduces the lines of code we need to support multiple
platforms from a project perspective.

Addtiionally, this heavily improves our detection of libraries, etc.