[forestTIME] Calculate carbon per acre and per "population"

[Aariq]

Actually not sure whether the code for this should live in forestTIME-builder or forestTIME.

• multiply carbon/tree by trees/acre (a quantity with three possible values determined by tree DBH)
• sum over some population (e.g. entire state, or subset of plots determined by arbitrary shape file)

[Aariq]

Dani is going to create a spreadsheet of "rules" for TPA expansion factor based on DESIGNCD and tree diameter. We can then merge this with the annualized tree table to get TPA for each tree for each year.

[Aariq]

Not going to get anywhere close to getting this done right now, so bumping to the next sprint and opening an issue about what I actually did on this project