Update blocktime for equihash (arrr & kmd)

source code has it hardcoded at 160 in stats.js line 589, and 250 in miner_stats.js at 250.

Each should be 60. or set as a  coin option variable. ("blockTime": 60,)

it gets calculations for luck much closer to real numbers.

Let me know if you see a problem with this or if i'm wrong.
