Update add-on to use libprojectM 4.x

[kblaschke]

This is a first, rough update to the add-on to make it work with the latest libprojectM 4.1 release. It runs fine on my Kodi on Linux. The build might need a few additional tweaks, as well as the settings dialog (e.g. adding more options supported by projectM), thus I'm initially creating it as a draft PR.

Note that libprojectM was almost completely rewritten between 4.0 and 4.1, with a new rendering process and expression parser. Due to the internal renderer updates, projectM now requires OpenGL ES 3.2 with the OES_texture_float extension being available. For OpenGL Core, at least GL version 3.3 is required (which is the same as before).

I don't think the depends dir is needed anymore, as libprojectM is now also built with CMake and thus can be found via CMAKE_PREFIX_PATH. This makes it more flexible, as (on Linux) maintainers can choose to use the distro package or compile libprojectM as static libs and directly embed it into the add-on shared library.

Also see my comment in the related issue #59 about Windows and Angle.

[kblaschke]

Oh, the build pipelines definitely also require some adjustments, e.g. build libprojectM beforehand.

On Windows/UWP, the add-on could in theory use vcpkg for that, as projectM has a port there. Not sure about how popular vcpkg is with Kodi development though.