[PATCH 6/7] New utility ubidump

[hujianyang]

> 
> If possible, please, try to implement few things at a time. Try to make
> your initial submission smaller, and then add more stuff on top. This
> way it is going to be easier to merge the work. Thanks!
>

I've resend the v2 patches. I spend a short vacation last week
and was busy with other stuff when I came back to work.

I think we can just apply binary data dump, ignore ubif/ubifs
format data at first to make initial submission smaller. How
do you feel about this?

just like:
ubidump /dev/ubiX_Y --lnum n

output binary/hex data.