New PR templates, contributing, scripts and bug fixes

This release contains feature additions that are accessory to the FATES code. These include a new PR template, a new CONTRIBUTING document and python scripts for manipulating FATES parameter files.
Bug fixes include a fix to biomass initialization during inventory (ckoven), removal of NPP partition tracking which will be re-introduced with the coming allocation refactor (rgknox), and a fix sapwood derivative calculation (rgknox/ekluzek).