FW-199,202. For CoAP GET reply, respect token and insert payload marker

Changes based on COAP draft 18 spec. Includes:
* Mirror up to COAP_MAX_TKL (8) byte token in GET reply
* Add payload marker if reply includes content
* Includes apps: layerdebug, r6tus, rinfo, rleds, rt, rwellknown, rxl1
* FW-202: Fix published uri-path for layerdebug neighbor app
Merge pull request #54 from kb2ma/FW-199c

FW-199,202. For CoAP GET reply, respect token and insert payload marker