Added CMEM as a model package

[HolmquistJ]

Description

This represents the first pull request integrating this model into PECAN. I have written several functions. R-version of the Cohort Marh Equilibrium Model (RCMEM) simulates plant ecology, elevation, and soil column evolution as a dynamic response to inundation. I have left met2model blank, given that there is currently no meteorological data inputs to MEM, just water level and tidal information. A model2netcdf function converts three data table outputs to netcdfs with time, latitude, longitude, depth, as species identifier as dimensions. A write.configs function currently receives parameters, initial condition, and driver files stored as model-specific Rds files and generates a model run. All functions currently work on a demo dataset and internal tests. Future steps will build out a demo workflow and generalize the model implementation to more readily accept new cite drivers and species parameters.

Motivation and Context

These changes were made due to requests from users to integrate models predicting tidal ecosystem state change due with sea-level rise and land use scenarios. Uncertainty in forecasts is important to restoration planning and carbon accounting.

Review Time Estimate

• Immediately
• Within one week
• When possible

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• My name is in the list of CITATION.cff
• I agree that PEcAn Project may distribute my contribution under any or all of
  • the same license as the existing code,
  • and/or the BSD 3-clause license.
• I have updated the CHANGELOG.md.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.