The previous broadcast model is replaced by a query-response one.
During normal operation, the cache of peers is not used anymore to select
peers to connect to. It now only used for bootstrapping and avoid querying
an already known address.

A lot of bug fix

Removing of the bandwidth calculation

When 2 tunnels are estabilshed between the same 2 peers, one of them is deleted

Check for dead tunnels evry 5 seconds instead of waiting for the next tunnel_refresh

Added exception catching in db, and modified utils.log so tht it can be used with anything ( and not only a string )