integrated review comments

I forgot to update one instance of "go-ethereum" in commit 3f047be5.

All code outside of cmd/ is licensed as LGPL. The headers
now reflect this by calling the whole work "the go-ethereum library".

* registar url string retrieval chop leading zeros now
* rewrite test using test mining
* remove temporary applyTxs from xeth

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

* 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

* BuyGas => SubGas
* RefundGas => AddGas
* SetGasPool => SetGasLimit

Removed the managed tx state from the chain manager to the transaction
pool where it's much easier to keep track of nonces (and manage them).
The transaction pool now also uses the queue and pending txs differently
where queued txs are now moved over to the pending queue (i.e. txs ready
for processing and propagation).

multiple contract source for solidity compiler: returns contract array if multiple contracts. fixes #1023