break ties and encourage closeness

     - Reduce exploratory tunnel quantity if build success rate
       is very low, but may disable this later
     - Try rebuilding same tunnel (some of the time)

    (ticket #542, see also http://zzz.i2p/topics/996)

    same-country peers; deduct for recently-unreachable peers

    - Increase default max connections again
    - Reduce min idle time
    - Separate out introducer pinger from introducer selection
      so it can be run separately and more often
    - Only ping introducers if we need them

    - Make most classes package private
    - Final, static, logs, cleanups
    - Consolideate createRateStat calls
    - Add getTotalLength()
    - Remove unused lengthOverride()

    - Refactor for concurrent, at some small risk of false negatives
    - Optimizations to cache objects and reuse offsets

     and 'cba0dcc238e5631aff5850f49d9cb07ec70e8f65'

  * Tunnels: Connection limit mitigation:
    - Disable tunnel testing
    - Implement closest-to-the-key tunnel selection
    - Use closest-selection in NetDB lookups, stores, and verifies;
      OCMOSJ; and in BuildRequestor

    fix udp.establishRejected stat