This is a preliminary fix for #420 (SEC-18 RLP decoder unsafe
allocation). If a sane input limit is set on the rlp.Stream,
it should no longer be possible to cause huge []byte allocations.

Whisper cleanup, part 2

p2p: fix the dial timer

The dial timer was not reset properly when the peer count reached
MaxPeers.

Fix RPC Call output when empty

Update transaction tests

Properly ignore blocks coming from peers not in our peer list (blocked)
and do never request anything from bad peers. Added some checks to
account for blocks known when requesting hashes (missing parents).

* Include tests which now has consistent HEX encodings
* Comment out two failing tests: "
  "TransactionWithHihghNonce" due to wrong nonce size
  "TransactionWithSvalueHigh" due to wrong ECDSA s range
* Cleanup conversion functions and fix expected encodings for
  tests validation fields

NOTE: For known, non-consensus, hard to reproduce bugs consider the
following method `common.Report("extra", stuff, "you need logged")` will
give you a stack trace and a friendly request to submit it as an issue
on our issue tracker.

Log filter `Address` field was cast to a Hash which causes it to always
fail.

All transaction and block messages are now limited using `sqrt(peers)`