• failover for both Ethereum and Decred.
• added CRC check for DAG files. Now if DAG file is corrupted, miner will detect it and re-create DAG.
  Don't remove DAG files manually if you think that they can be corrupted - miner will do it automatically if necessary.
• default value for "-ethi" option is "8" now (instead of "16"), it slightly reduces delays when miner accepts new job.
• Bug fixes, a few minor improvements.