skyward-boardcore

* CMake file for SBS (sbs.cmake) contains function 'sbs_target', that allows to configure an SBS target (entrypoint or test).

* CMake file for dependencies (dependencies.cmake) contains definitions wrt. dependencies, including Skyward Boardcore sources (previously defined in sbs.conf).

* Find Module files allow CMake to find packages, including libraries (Eigen, {fmt}, Mxgui and TSCPP).

* At the moment, to make Find Module file for {fmt} work it is needed to run `make` in libs/fmt before configuring.

* Find Module file for Mxgui is not fully working yet.

* Skyward Build System v2.0 files are removed, as they are replaced by v3.0 files.