CMake builds are always RELEASE builds

Created by: siebenkopf

Just to keep track: Currently, compiling a Library with CMake always uses -DCMAKE_BUILD_TYPE=RELEASE, even when debug option is set in the options. A check for these options need to be implemented.

Also, the compiler between the Python extensions and the C++ libraries might differ. Maybe we should try to unify them. First trials showed that this might not be that easy...