Fix a couple of OLSR bugs (#415)
- Added a lot more logging messages;
- When "link sensing" tries to update a link tuple for a neighbor that has been removed, just re-add the neighbor, rather than silently failing;
- The optimization of not recomputing the routing table if we think no state has changed has been removed: it turned out to be just too buggy and the code base makes it difficult to catch all places where a state mofication is done. Instead now we just recompute the table for any message processed, like the RFC says.