add info on generation of MPB climatic suitability maps

[achubaty]

@BarryCooke

mpb-maps/climate-projections.Rmd needs to be updated to explain the generated maps.

• How were these generated, and how can they be regenerated as needed? Include scripts/code.

• What do the maps represent, exactly? What do the raster values mean and how should they be interpreted?

  The response is a float number which can be used as a climatic multiplier on MPB baseline reproductive rate.

  Not sure if this is totally accurate, since values aren't bound between [0, 1].

• What are the caveats to using these maps (i.e., assumptions, limitations, etc.)?

• What is the availability of the maps and their underlying data? Are they publicly available? From where can they be downloaded? With whom can they be shared?

[achubaty]

@BarryCooke I need this info ASAP. Ideally, we can get a reporducible way to regenerate these maps to produce annual climate suitability layers.

[achubaty]

Mathieu Fortin's BioSIM R package and corresponding BioSIM web API creates annual MPB SLR indices (and many more!)

https://sourceforge.net/p/mrnfforesttools/biosimclient/wiki/BioSIM-R/

We will move to using these instead of the pregenerated maps from years ago. Closing.