this PR to update uip-ds.h comments, this small change is made to ease the track of Tables implementation places
remove definition of UIP_CONF_DS6_ROUTE_NBU
retire 2 old macros DS6_NBR_NBU, DS6_ROUTE_NBU
Update uip-ds6.h
Update contiki-conf.h
Update contiki-conf.h
Update contiki-conf.h
fix doxygen comment
Update uip-ds6.h