Feature 293 figure dir

[lisagoodrich]

Pull Request Testing

• Describe testing already performed for these changes:
  I have moved all the .png images into a "figure" directory to match the formatting across other METplus projects. There were 48 images. They needed to be updated in 19 rst files (listed below).
  I have reviewed the images and confirmed all of the image locations have been updated.
  I didn't receive any warning logs once all of the files were updated.
  This is the command I used to locate all of the image files. (Please note, it does yield some extra results.).
  grep "image" *.rst

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  Below is a listing of the 19 files that were changed and the number of images that were updated. I checked and all of the files were there and matched the "latest" branch. Please do a quick check to confirm this.
  Here is a link to the feature branch where the changes were made: https://metplotpy.readthedocs.io/en/feature_293_figure_dir/Users_Guide/line.html
  bar.rst: 1 image
  box.rst: 2 images
  contour.rst:.. 2 images
  difficulty_index.rst: 6 images
  eclv.rst: 2 images
  ens_ss.rst: 1 image
  fv3_physics.rst:5 images
  histogram_2d.rst: 2 images
  histogram.rst: 6 images
  hovmoeller.rst: 2 images
  line.rst: 2 images
  performance_diagram.rst: 3 images
  polar_plot.rst: 3 images
  reliability_diagram.rst: 2 images
  roc_diagram.rst:.2 images
  Sstratosphere_diagnostics.rst: 4 images
  taylor_diagram.rst: 4 images
  tcrmw_cross_section.rst: 1 image
  wind_rose.rst: 3 images

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes or No]. There are no errors in the documentation.

• Do these changes include sufficient testing updates? [Yes]

• Will this PR result in changes to the test suite? [No]
  
  If yes, describe the new output and/or changes to the existing output:
  

• Please complete this pull request review by [2/28/23].
  

Pull Request Checklist

See the METplus Workflow for details.

• Review the source issue metadata (required labels, projects, and milestone).
• Complete the PR definition above.
• Ensure the PR title matches the feature or bugfix branch name.
• Define the PR metadata, as permissions allow.
  Select: Reviewer(s)
  Select: Organization level software support Project or Repository level development cycle Project
  Select: Milestone as the version that will include these changes
• After submitting the PR, select Development with the original issue number.
• After the PR is approved, merge your changes. If permissions do not allow this, request that the reviewer do the merge.
• Close the linked issue and delete your feature or bugfix branch from GitHub.

[bikegeek]

Looks good.