Introduced a cleaned-up cpu/core interface

In attempt of a clean-up for the interface between the core and platform (cpu) specific code I introduced an interface-collection, that extracts all platform dependent interfaces from the core into a single location (folder).

The PR can not be merged yet -> i doesn't build because the cpu implementations are not yet adapted!

But the PR can maybe help to start a short discussion if the interfaces make sense and if we should further pursue this approach...