gnrc: rename ng_netbase to gnrc

Makefile.dep

Makefile.pseudomodules

cpu/nrf51/radio/nrfmin/nrfmin.c

drivers/at86rf2xx/at86rf2xx.c

drivers/at86rf2xx/at86rf2xx_netdev.c

drivers/include/xbee.h

drivers/kw2xrf/kw2xrf.c

examples/gnrc_networking/udp.c

sys/Makefile

sys/auto_init/netif/auto_init_at86rf2xx.c

sys/auto_init/netif/auto_init_kw2xrf.c

sys/auto_init/netif/auto_init_ng_netdev_eth.c

sys/auto_init/netif/auto_init_slip.c

sys/auto_init/netif/auto_init_xbee.c

sys/include/net/gnrc.h

sys/include/net/ng_ipv6.h

sys/include/net/ng_slip.h

sys/include/net/ng_udp.h

sys/net/application_layer/ng_zep/ng_zep.c

sys/net/crosslayer/ng_pktdump/ng_pktdump.c