Automatic cleaning of the JFFS2 partition (overlay) at the first start

[ZigFisher]

[ZigFisher]

random: fast init done
jffs2: Incompatible feature node (0xe008) found at offset 0x00539a68
mount: mounting /dev/mtdblock4 on /overlay failed: I/O error
mount: mounting ubi0:rootfs_data on /overlay failed: No such device
Starting syslogd: OK

[cronyx]

improved in #262