Feature/c make update
I reviewed and updated the whole CMake build system to be a bit cleaner and more consistent. I tried to avoid changing any of the visible behaviours but there are a few things to consider:
- I kept the root minimal version to root 6 but I think it would be better to bump that up to 6.14, as before that version a lot of the CMake machinery in ROOT was kind of broken
- The required versions for GSL and Open MP are missing
- I tried to separate the different projects which actually make up Garfield. For Magboltz and Nebem it is relatively easy but Heed, as packaged, has some interdependencies with Garfield. This should be analyzed and addressed in the future
- I didn't move the heed DB install folder but I think it should. I think it should be moved in the standard data folder common to the linux packaging infrastructure (/share/Heed)
- I changed the exported CMake configuration files to complete rely on the target base system of CMake 3 and I added the correct dependency search macro to the config file
- The installation folder of the CMake configuration files are cheanged to share/Garfield/CMake as this is the only search path that is common to all platforms
- All the examples now DO NOT create a separate project within the project