require explicit etherbase address for mining. Falling back to primary is risky given it is inconsistent if keys are imported/merged/created or copied/transfered

* multiple passwords allowed in password file
* split on "\n", sideeffect: chop trailing slashes. fixes common mistake <(echo 'pass')
* remove accounts.Primary method
* do not fall back to primary account for mining

core, xeth: core.AddressFromMessage removed => crypto.CreateAddress

Implement eth/61

core, cmd/geth: improved recover functionality

`geth recover` now accepts both hashes and numbers using "#" and no
longer requires the ethereum instance.

core, cmd/geth: recover by number

Use uint64 for block header timestamp

fix logging jsonrpc request #1365

core: added checkpoint for last block

Changed the transaction pool to listen for ChainHeadEvent when resetting
the state instead of ChainEvent. It makes very little sense to burst
through transactions while we are catching up (e.g., have more than one
block to process)

* Add a checkpoint every X blocks
* Removed queued write

Add pendingTransactions and resend

core: reduce CPU load by reducing calls to checkQueue

* Reduced maxQueue count
* Added proper deletion past maxQueue limit
* Added cheap stats method to txpool

queueCheck was called for **every** transaction instead of:
1. add all txs
2. check queue

previously

1. add txs[i]
2. check queue
3. if i < len(txs) goto 1.