bin/adb-backup-system: add a no sdcard option
bin/adb-restore-bare-data: add a no-sdcard variant
bin/xscreensaver-watcher: add 2 hooks to decouple it
etc/adb-sync-data-exclude: add some more files that should not sync

Signed-off-by: Bao Haojun <baohaojun@gmail.com>