Show tahoe-lafs introducer on about screen

src/freedombone-controlpanel

     echo ''
 }
 
+function show_tahoelafs_introducer {
+    INTRODUCER_FILENAME=cat /home/tahoelafs/data/private/introducer.furl
+    if [ ! -f $INTRODUCER_FILENAME ]; then
+        return
+    fi
+    echo $'Tahoe-LAFS introducer'
+    echo '====================='
+    echo ''
+    echo "$(cat $INTRODUCER_FILENAME)"
+    echo ''
+    echo ''
+}
+
 function show_about {
     clear
     echo ''
     show_tor_bridges
     show_ssh_public_key
     show_domains
+    show_tahoelafs_introducer
     show_mirrors_password
     show_tahoe_introducer
     show_users