This commit cleans up the reuse port setup, and fixes a problem:
make sure to filter addrs out that we simply cannot dial with
(e.g. loopback -> non-loopback, or linklocal -> nonlinklocal)

This commit finally makes use of the sent observed addrs.
If the connection's local address is from one of our
listen addrs, then the remote's observed addr is its
natted mapping, which is useful to us. For now, we add
it directly to our address book. (a future commit should
make addressbook addresses expire)

fix(bitswap.decision.Engine) send only the freshest messages

@whyrusleeping

Before, the engine worker would pop a task and block on send to the
bitswap worker even if the bitswap worker wasn't to receive. Since the
task could have been invalidated during this blocking send, a small
number of stale (already acquired) blocks would be send to partners.

Now, tasks are only popped off of the queue when bitswap is ready to
send them over the wire. This is accomplished by removing the
outboxChanBuffer and implementing a two-phase communication sequence.

fix fuse mounting issues

This commit moves the record validation/verification
from dht/ into the new record/ packaage. Validator object
-- which is merely a map of ValidatorFuncs -- with a
VerifyRecord

cc @whyrusleeping

this time, without loading the private key on every startup

feat(bitswap.decision.Engine) use PriorityQueue for Engine.Outbox

	refactor: peerRequestQueue

	it's a mistake to make one queue to fit all. Go's lack of algebraic
	types turns a generalized queue into a monstrosity of type
	checking/casting. Better to have individual queues for individual
	purposes.

	Conflicts:
		exchange/bitswap/decision/bench_test.go
		exchange/bitswap/decision/tasks/task_queue.go

	fix(bitswap.decision.PRQ): if peers match, always return result of pri comparison

	fix(bitswap.decision.Engine): push to the queue before notifying

	TOCTOU bug

	1. client notifies
	2. worker checks (finds nil)
	3. worker sleeps
	3. client pushes (worker missed the update)

	test(PQ): improve documentation and add test

	test(bitswap.decision.Engine): handling received messages

	License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

Conflicts:
	exchange/bitswap/decision/taskqueue.go

feat(core) replace config.Config with repo.Repo

@jbenet cool with this?

This declarative style is simpler to compose than the imperative wiring
up of objects.

+ pass context to StartOnlineServices as parameter. one by one, trying
to remove dependencies on node state so these initialization steps can
be broken down.

@jbenet wasn't sure about the terminology here. I'm certain what I wrote
is not entirely correct. Feel free to edit.

@whyrusleeping @jbenet does passing this argument effectively instruct
the dagbuilder to pin recursively?