crossplatform build

[mathisloge]

So this is mostly the same as for node-mapnik.
It replaces most of the python build code with a cmake file.

It depends on mapnik/mapnik#4191

via the find_package(mapnik) all compile options and paths to fonts/plugins are available. I dont use mason, so if someone depends on that, someone needs do describe the steps to get mason up and running.

In the end, the whole vcpkg submodule can be removed again. Just here for faster development.
If someone needs to build from source, one can just add a local clone of vcpkg via -DCMAKE_TOOLCHAIN_FILE=<path to vcpkg toolchain>.

I'm just waiting for some feedback on this, before putting more effort into it.

Todos:

• i think fonts needs to be installed without subdirs? currently it looks like mapnik/lib/fonts/dejavu-fonts-ttf-2.37/ttf
• test on ubuntu
• have someone a mac to test with? I have zero experience with mac and don't have one at home.

Some first results on windows-10:

rendered with cairo:

[mathisloge]

and code changes depend on mapnik/node-mapnik#975