Revert "Included update_number in the network hash (draft needs update too)."

This reverts commit 40dbfcce9dca6e6e02292ef41b56f1404343d947.
First attempt at unifying the update_number + tlv data handling logic to make the schedule/flag handling sane.
Fixed net_sim's sanity check to actually skip node data header.
Addressed errors in bird14 - as we remove+add _same_ node, winding up with same update#, but some differences in time is probably acceptable given current design.
Some logic/debug message cleanup efforts. Still failling but very, very rarely now.
Added ignoring of data for unreachable nodes at the moment (should not really matter but perfectionism..)
Updated comments to be bit more accurate in how neighbors are handled in hncp.c.
As we want to establish bidirectional reachability asap (and do not want to keep unreachable initial neighbors around long), send immediate unicast ping and pretend after that we're in the ping expiration mode until we get first unicast response.