Feature 2463 modify table (#2508)

* creating test dropdown menus

* fixing warnings

* fixing warnings

* fixing warnings 3

* fixing warnings 4

* Attempt to fix documentation errors

* adding 2 more test dropdowns

please note.  There is still a message about 
WARNING: Duplicate explicit target name: "gridstat: cloud fractions with neighborhood and probabilities (pygrib)".
John O will fix this.  I should not touch it.

* fixing spacing

* trying to fix link

* take 2

* Removing double underscores added earlier

* moving dropdown menus

* Adding version to dropdown menu title

* fixing spacing

* dropdowns date util, eofs, h5py

* fixing formatting

* fixing formatting

* Per #2463, adding template for future entries

* adding imageio, lxml & matplotlib

* dropdown up to nc-time-axis

* fixing spacing problems

* Fixing broken s2s links and other incorrect links

* Fixing spelling and capitalization

* Removing the dash in front of 1.4 for nc-time-axis

* Modifying formatting

* adding dropdowns thru pylab

* fixing problems

* dropdowns thru scikit-learn

* fixing spacing

* final dropdowns thru yaml

* fixing spacing

* fixing loose ends

* Per #2463, moving information to an Appendix and adding text and links in an overview

* Per #2463, adding to index.rst

* Per #2463, reworded language and updated Python 3.8 reference

* Per #2463, fixing errors

* Per #2463, made updates based on feedback at the METplus Engineering meeting.

* removing tables, changing most METplus wrappers, version numbers.

* trying to fix met_version

* Per #2463, adding necessary code for substitutions

* Per #2463, fixing syntax error

* adding period

* removing section 1.5

* Per #2463, replace old label reference with new label reference and updated text to reflect the move to drop down menus

* read python version from file to replace in docs

* fixed typo in variable name

* adding python_version to the overview.

---------

Co-authored-by: Julie Prestopnik <jpresto@ucar.edu>
Co-authored-by: George McCabe <23407799+georgemccabe@users.noreply.github.com>

docs/Contributors_Guide/add_use_case.rst

@@ -223,11 +223,11 @@ use case OR category directory for a model_applications use case
     * Update the description of the input data in the Datasets section.
 
     * Update the list of External Dependencies (if applicable) to include any
-      required Python packages.  Update the :ref:`python_requirements_table`
-      table.  If the package is already listed in the spreadsheet, add
-      a link to the documentation page for this new use case, following the
-      format in the table.  If the package is not already listed, update
-      the table to include the name of the required package, the version,
+      required Python packages.  Update the :ref:`components_python_packages`
+      section.  If the package is already listed, add a link to the documentation
+      page for this new use case in the dropdown menu for that package, following the
+      format in the dropdown menu.  If the package is not already listed, update
+      the dropdown menus to include the name of the required package, the version,
       the METplus component (e.g. METplus wrappers, METcalcpy, METplotpy), the
       source, a brief description of the package, and a link to this new use
       case that uses this new Python package.