Update difference map bins to split around zero - and other minor updates

Description & motivation

The following changes update the difference map bins in process_defintions.R to split around zero. This change was requested by restoration project planning partners who use outputs generated by this repository. The middle bin was split in to 3 bins with "0" in the middle. All other difference map bins were left as is. The difference bin color ramp was also expanded by 2 colors to accommodate the additional bins. The viridis yellow that we use is set to the "0" bin. The changes to the color ramp are found in the xx_map_functions.R files.

I also tested the BBSEER AOI to ensure proper mapping layout.

While updating the difference bins and testing the AOI I noticed a few random items to update:

• Update individual map cut function to be right-handed: Cut values and labels are inprocess_definitions.R. The application of these cut values and labels is in rest_run_process_function.R
• Update rest_run_map_functions.R and smallfish_map_functions.R to set map extent limits based on provided AOI shapefile - this should enable more dynamic plotting between projects
• Update scale bar placement in smallfish_map_functions.R to be dynamic based on AOI extent
• Add white box behind scale bar to increase readability: rest_run_map_functions.R. This should help when the scalebar falls on top of lines used to show the Everglades areas boundaries
• Update pattern matching for marl prairie files to be more dynamic: marlprairie_workflow.R
• Add missing ggpp package to smallfish_map_functions.R
• remove hist() and calculate acreage for difference bins generated using cut(): marlprairie_process_function.R and rest_run_process_functions.R

Notes for peer reviewers: 

Review Timeline: It would be helpful if this review could be completed by Friday, December 1st.

@shaider @ldacunto @abenscoter Can someone please review these changes. Specifically, please review the breaks and labels used to generate maps:

1. Updated difference map breaks and the associated labels in process_definitions.R. These should match a left-hand break (For reference, the left-hand break is found in the workflow at the following locations rest_run_process_functions.R line 284, smallfish_workflow.R line 347, marlprairie_process_function.R line 81)
2. Individual map breaks for Alligator, Snail Kite, waders, and DSD. These should match a right-hand break (For reference, the right-hand break is found in the workflow at the following locations rest_run_process_functions.R line 279)

I will share a OneDrive folder that has some sample data if you want it for anything.

Checklist:

• I have outlined my changes in the CHANGELOG. 
• Update CHANGELOG date if changes are made during review.
  • N/A - No changes made during review.
• My merge request represents one logical piece of work.
• My R code follows our style guidelines. 

 To do after merge 

• Create a new tag using the date, version number, and description of the changes from the CHANGELOG