getTransactionReceipt RPC support

Fix core errors in apply txs

core, core/state: throw out intermediate state

Account management improvements

* Update => SyncIntermediate
* Added SyncObjects

SyncIntermediate only updates whatever has changed, but, as a side
effect, requires much more disk space.

SyncObjects will only sync whatever is required for a block and will not
save intermediate state to disk. As drawback this requires more time
when more txs come in.

core, eth, miner, xeth: receipt storage fix

* Added GetReceiptsFromBlock, GetReceipt, PutReceipts
* Added ContractAddress to receipt. See #1042

Update Ethereum JSON test files, skip failing tests

Upgrade web3 to version 0.7.1

Several bugfixes to IPC channel

miner: ignore future errors

core, miner: miner header validation, transaction & receipt writing

Prevent false from printing on console

* Miners do now verify their own header, not their state.
* Changed old putTx and putReceipts to be exported
* Moved writing of transactions and receipts out of the block processer
  in to the chain manager. Closes #1386
* Miner post ChainHeadEvent & ChainEvent. Closes #1388

eth/downloader: fix a rare test race on the OSX CI

* account.Update
* KeyStore.Cleanup
* fix dir rm for old format deleteKey

* chronological order of creation
* new naming scheme keystore/UTC--<created_at UTC ISO8601>-<address hex>
* KeyStore2 -> KeyStore
* backward compatibility
* refactor keyStore methods