model diagnostics

[achubaty]

I've pulled Ian's diagnostic plot functions from the scfm.Rmd file, adatped them for use in scfmutils, and have impelmented a simple module for diagnotic plotting (scfmDiagnostics) that gets scheduled to run and the end of the simulation and can also be run in postprocessing to summarize multiple runs.

• map showing the fire regime polygons used
• estimated vs simulated fire return interval
• estimated vs simulated ignitions
• estimated vs simulated mean fire size
• estimated vs simulated escapes
• cumulative burn map (also showing flammability)