Add license to each file for clarity

apps/decawave-demo/dw-sync-demo.c

apps/decawave-range/dw-range-anchor.c

apps/decawave-range/dw-range-tag.c

apps/decawave-range/dw-range.c

apps/decawave-range/dw-range.h

apps/decawave-range/dwFrameTypes.c

apps/decawave-range/dwFrameTypes.h

src/dw1000-base.c

src/dw1000-base.h

src/dw1000-hal.h

src/dw1000-spi.c

src/dw1000-spi.h

src/example.h

src/platform/mulle/mulle-hal.c

src/platform/mulle/mulle-spi.c