fire_forward streamlined to filter by polygon, including pre and postprocessing steps

Workflow to integrate run function that constrains pixels by a fire perimeter and runs fire_forward.

To do list:

• change carb_run function names to something more general (e.g. RunShapeConstrain)
• remove carb_run.py file and add functions to FireRun.py file
• in carb_run functions, remove year parameter and make tst/ted optional. When tst/ted provided, overrides tst/ted in polygon file
• make tst/ted optional in FireTime.update_tst_ted()
• in postprocess, change year parameter to tst parameter so it's more familiar
• see if you can use save_large_fires_layers() instead of creating save_individual_fire()
• understand why you might want to keep invalid fires around when saving individual fires