Add fixtimes utility

The directories in the whiteboard export have invalid modification
timestamps, this script "fixes" them, by setting them to the current
time.

fufixtimes.sh

+#! /bin/sh
+
+if [ ! -f 'grades.csv' ]; then
+    printf "Execute within the directory containing 'grades.csv'\n" >&2
+    exit 1
+fi
+
+find . -exec touch {} \;

install.sh

 #! /bin/sh
 
-scripts="fixpdf.sh fucopy.sh fufixpdf.sh fuzip.sh fuxournalexport.sh"
+scripts="fixpdf.sh fucopy.sh fufixpdf.sh fuzip.sh fuxournalexport.sh fixtimes.sh"
 
 destdir="${DESTDIR:=$HOME/.local/bin}"
 mkdir -p "$destdir"