General fixes

* Changed CalcGasLimit to no longer need current block
* Added a gas * price + value on tx validation
* Transactions in the pool are now re-validated once every X

eth, eth/downloader: improve downloader and remove asynchronousness

Fix ignore of unexpected files in key dir

Transactions will be invalidated when the tx.gas_limit > block.gas_limit

core: fixed wildcard topic filters. Closes #725

CLI and JS admin changes

Simpler "welcome"

cli/js console: if corsDomain is not given to startRpc, we fall back to value set on command line with `-corsDomain`

cli: clean up flag descriptions, usage docs, account list uses primary and indexes, add help line to account subcnd usage

Ethereum js update

Bootnodes update