potential restructuring

[teixeirak]

@ValentineHerr , I'm starting this issue to note some ideas (perhaps bad ones!) for improving the ForC structure in a later phase of the IPCC project:

1. Create a combined sites/plots table, with a single unique ID for each linked to measurements. This would make it much easier to review and merge duplicates, and we could still retain the structure of plots nested within sites.
2. It might help to move some of what's in the measurements table to a plots or history table: e.g., vegetation type, age, etc., along with year described. This would avoid meaningless repetition and could solve some of the problems associated with trying to assign an exact stand.age to each measurement in stands with poorly defined age.