Synthesis Post-Processing: Adding derived stocks for each core

[jaxinewolfe]

Proposal to add columns to the core-level table which contain the calculated stocks for (1) each core in its entirety, and (2) each core from 1 to 100cm (extrapolation from 50cm up if the core is shorter than 100cm, or cutting of at 100cm if the core is longer).

[jaxinewolfe]

@HolmquistJ I see this coming up consistently as a want from the research community that are end-users of the Atlas. I think adding these two derived columns (or something of that nature) to the core-level table could increase it's utility to more end-users while maintaining the interfaces functional ability to serve disaggregated data. These end-users are namely the ones who are interested in the core-level data, happy to use our calculated stock values at that resolution, and may not have the bandwidth to download and perform these calculations on the depthseries table themselves. We can provide our methods in the download.