Photon^1 (v0.4.1)

iotex-core v0.4.1 is a patch release that contains the following bug fixes:

• Improve the block sync logic to proactively ask for higher block if a not doesn't observe incoming blocks for a while;
• Fix action injector to be able to inject 1K+ tps workload;
• Fix nonce validation bug;
• Make block interval calculation always be based on the last block timestamp.