analyze/ reconcile past status codes

[teixeirak]

@ValentineHerr , this file is very helpful in that it provides the record of past status codes for each tree. It would be helpful to create this for all trees and do a bit of analysis to detect errors.

It's particularly interesting to look at trees previously considered dead that were later found alive. There seem to be a fair number of cases from the 2018 main census. I wonder if some of these trees were censused in the early spring or late fall when it was hard to tell the difference between dead and live with leaf-off.