[bin][doc] remove obsolete merge_cpp_and_md.sh

bin/doc/merge_cpp_and_md.sh

-#!/bin/sh
-
-# check if help is needed
-if test "$1" = "--help" || test "$1" = "-help" \
-   || test "$1" = "help" || test "$1" = ""; then
-  echo ""
-  echo "USAGE: $0 FILENAME_1 [FILENAME_2 ...]"
-  echo ""
-  echo "The arguments should be names of Markdown and/or C++ files."
-  echo "The script loops through all arguments. If a Markdown file is encountered,"
-  echo "its content is forwarded to stdout. For another file, a Markdown header"
-  echo "stating the filename is printed and the script cpp_to_md.sh is applied."
-  echo "To be used for creating README.mds in the example folder. For example, by"
-  echo "bash $0 intro.md spatialparams.hh problem.hh main.cc results.md >README.md"
-  exit 0
-fi
-
-for filename in "$@"
-do
-  if [[ ${filename: -3} == ".md" ]]; then
-    cat $filename
-  else
-    echo ""
-    echo ""
-    echo "## The file \`$filename\`"
-    echo ""
-    bash cpp_to_md.sh $filename
-    echo ""
-  fi
-done