Default gasprice + new rpc methods
Default gasprice + new rpc methods

- geth will ignore a transaction with a low gasprice and blacklist the
user, this caused trouble because the default gasprice used in the
deploy_solidity_contract method was 1 wei.
- pooling didn't account for the removal of a transaction (that can be
caused by the low gas price)
- added new rpc methods:
  - eth_estimateGas
  - eth_getTransactionReceipt
  - eth_getCode
- added a utility for the Proxy to get the estimated gas usage.

ethereum/pyethapp,changwu-tw/pyethapp,changwu-tw/pyethapp,ethereum/pyethapp,gsalgado/pyethapp,gsalgado/pyethapp