Use dist Makefile style in examples Makefiles
dist/example Makefiles: not BOARD -> no BOARD, ## Modules -> # Modules
remove trailing slashes from RIOTBASE variables

addresses https://github.com/RIOT-OS/RIOT/pull/496#issuecomment-32170092
Merge pull request #496 from LudwigOrtmann/examples_cleanup

Example/dist Makefile cleanup