* don't accept zero difficulty jobs * bound job queue * synchronous emit_payload * cleaner gpu_batch_size type * remove build script * distance_threshold -> difficulty * enable pq-cert checking with miner * clearer logs * Revert "enable pq-cert checking with miner" This reverts commit 7a7f5394352b60d8c946f547f77a057504b29c44. * update versions of relevant deps, including rand