implementing draft-thubert-6man-flow-label-for-rpl-03
adding missing function to the simulator
little debug traces and code clean
FW-224 fixing loop detection error logs.
Merge pull request #63 from openwsn-berkeley/develop_draft_flowlabel

 FW-224. draft-thubert-6man-flow-label-for-rpl-03
Merge branch 'develop' into develop_FW-229
FW-229. Declaring the right files to compile.
FW-229. Fixing build.