Fix issue: num_decimals = 0, should be 18

[trentmc]

DataTokenTemplate.sol needs decimals to be able to support AMMs like Balancer and Uniswap. Balancer is currently the leading contender to make marketplace non-custodial and to support marketplace incentives. I encountered this issue first hand this week while doing Balancer experiments (I did a workaround in my branch by fudging the file to 18 decimals). Details of why are in this V3 slide.

I recommend 18 decimals because that's what ETH and OCEAN have (as most other tokens). It allows library conversion commands fromWei() and toWei().