added spark core board

- [x] based on https://github.com/RIOT-OS/RIOT/pull/1752 <- wait for its merge first!

TODO:
- [x] test
- [x] restore examples/hello-world
- [ ] extend blacklists
- [x] add flash/debug scripts and make targets
- [ ] update wiki
- [ ] fix doxygen/authorship
done (not shown by github)