Replace should_i_rebuild.sh by a new script that corresponds to what we do in the current cron job nowadays

rebuild.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+workdir=$(dirname "$0")
+log=$workdir/app_list_auto_update.log
+
+cd $workdir
+date >> $log
+git pull >/dev/null
+
+python ./list_builder.py &>> $log || sendxmpppy "[listbuilder] Rebuilding the application list failed miserably"