6lowpan ESC Dispatch Code Points and Guidelines

RFC4944 defines the ESC dispatch type to allow for additional dispatch octets in the 6lowpan header. The value of the ESC dispatch type was updated by RFC6282, however, its usage was not defined either in RFC6282 or in RFC4944. This document updates RFC4944 and RFC6282 by defining the ESC extension octet code points including registration of entries for known use cases at the time of writing of this document.