Need improvements of get blocks/headers RPC APIs

[trinhdn97]

• The format of data field in event logs is not consistent between tx_getTransactionReceipt and other filter APIs. The log data returned by tx_getTransactionReceipt API is prefix with 0x while other filter APIs don't return the logs data with any prefix.
• The "latest" header/block/state should not be the CurrentBlock which is processing in consensus manager. For example, the HeaderByNumber is curently implemented as below

func (k *KardiaService) HeaderByNumber(ctx context.Context, number rpc.BlockNumber) *types.Header {
	// Return the latest block if rpc.LatestBlockNumber has been passed in
	if number == rpc.LatestBlockNumber {
		return k.blockchain.CurrentBlock().Header()
	}
	return k.blockchain.GetHeaderByHeight(number.Uint64())
}

The "latest" header should be the header before k.blockchain.CurrentBlock().Header(). That CurrentBlock in KardiaChain network is equal to "pending" block in Ethereum network, which is processing by miners. The same for "latest" block and state.

• The block hash field of get blocks/headers by hash RPC APIs should allow "earliest", "pending" and "latest" keyword for convinient.

[trinhdn97]

Resolved in #143