Merge pull request #9184 from haukepetersen/add_mynewt_nimble

cpu/nrf5x_common/include/nrfx.h

examples/nimble_gatt/Makefile

examples/nimble_gatt/README.md

examples/nimble_gatt/main.c

pkg/nimble/Makefile

pkg/nimble/Makefile.dep

pkg/nimble/Makefile.include

pkg/nimble/contrib/Makefile

pkg/nimble/contrib/controller_init.c

pkg/nimble/contrib/include/nimble_riot.h

pkg/nimble/controller.mk

pkg/nimble/doc.txt

pkg/nimble/drivers.nrf52.mk

pkg/nimble/ext.tinycrypt.mk

pkg/nimble/nimble.host.mk

pkg/nimble/nimble.host.store.ram.mk

pkg/nimble/nimble.host.util.mk

pkg/nimble/nimble.mk

pkg/nimble/porting.nimble.mk

pkg/nimble/porting.npl.riot.mk