Split check-no-floating.sh into multiple files.

Closes #479 (closed)

doc.zih.tu-dresden.de/util/check-every-page-not-included-more-than-once.sh

+#!/bin/bash
+scriptpath=${BASH_SOURCE[0]}
+basedir=$(dirname "${scriptpath}")
+basedir=$(dirname "${basedir}")
+DOCUMENT_ROOT=${basedir}/docs
+
+MSG=$(find ${DOCUMENT_ROOT} -name "*.md" | while IFS=' ' read string
+  do
+    md=${string#${DOCUMENT_ROOT}/}
+
+    # count occurences of md in nav 
+    numberOfReferences=$(sed -n '/nav:/,/^$/p' ${basedir}/mkdocs.yml \
+      | grep -c ${md})
+    if [[ ${numberOfReferences} -gt 1 ]]; then
+      echo "${md} is included ${numberOfReferences} times in nav"
+    fi
+  done
+)
+if [[ ! -z "${MSG}" ]]; then
+  echo "${MSG}"
+  exit 1
+fi