The address manager now guarantees the goal #4 and #6:

 4. Make sure no attacker can fill the entire table with nodes/addresses
    he controls (assume nodes are geographically close).
 6. Serve addresses that are geographically spread
The address manager now guarantees the goal #3:

 3. Any peer cannot have more than X% of the addrs added by him
Announce more addresses if in response of a getaddrs command.
Now the address manager does a periodic bucket cleanup.
Added a bunch of metadata to Cargo.toml.
Address manager now drops old addresses, effectively implementing this:

  * (2) Drop old addresses (with >= X hrs)
    * (1,2) To drop addresses select older

There are a few related things to do, like update addresses timestamp.
We know update addresses timestamps.
Address manager now has high-level logging.
Merge branch 'addr-mng-decent'.