do_mirror.sh: Support multiple entries in BASE_SYNC

Signed-off-by: Gianpaolo Macario <gianpaolo_macario@mentor.com>
Add (commented) sample entry for BASE_SYNC
do_mirror.sh: Add --delete --progress options to rsync
Merge pull request #29 from gmacario/multiple-entries-basesync

Add support for multiple entries in BASE_SYNC