Update FOIA patch spreadsheet instructions for xlsx2csv error case

The VA FOIA site's 2013 spreadsheet does not convert directly from .xls
to .csv with xlsx2csv.  It needs MS Excel to convert to .xlsx first.
Note this possibility in the instructions.
Add VA VistA FOIA patch 2013 spreadsheet

Follow the instructions in 'Scripts/HowtoUpdateSpreadsheets.rst' to add
'Packages/Uncategorized/*.csv' spreadsheets corresponding to:

 https://downloads.va.gov/files/FOIA/Software/DBA_VistA_FOIA_System_Files/Listing_of_Released_VistA_Patches_2013.xls

Remove the leading "ALL DOCUMENTATION..." row so the first row has the
column names.  Remove extra rows from the bottom.
Merge branch 'upstream-spreadsheets'
Add Patches/<package>/README.rst files

Add a README.rst to each package directory to document its purpose and
reference the top-level README.rst file.  This will aid users that
arrive in a repository browser through a link pointing directly at a
package directory.

Use the following shell code to create the files from Packages.csv:

tail -n +2 Packages.csv |
egrep '^[^,]+' |
while IFS=, read pkg dir _; do
  mkdir -p "Packages/$dir" &&
  hdr="VistA: $pkg"
  line="$(echo "$hdr"|sed 's/./=/g')" &&
  readme="Packages/$dir/README.rst" &&
  echo >"$readme" \
"$line
$hdr
$line"'

This directory facilitates development and distribution of a VistA package.

See `<../../README.rst>`__ for more information.

-------
Patches
-------

The `<Patches>`__ directory contains patch host files for the package
organized into subdirectories named for each patch.'
done
Add Patches/<package>/Patches/README.rst files

Add a README.rst to each package Patches directory to document its
purpose and reference the package README.rst file.  This will aid users
that arrive in a repository browser through a link pointing directly at
a package Patches directory.

Use the following shell code to create the files from Packages.csv:

tail -n +2 Packages.csv |
egrep '^[^,]+' |
while IFS=, read pkg dir _; do
  mkdir -p "Packages/$dir/Patches" &&
  echo >"Packages/$dir/Patches/README.rst" \
'This directory contains patch host files for a VistA package.
The files are organized into subdirectories named for each patch.

See `<../README.rst>`__ for package details.'
done