Added updating information for the offline wallet from an unsigned saved transaction.

Hello, I have sent an issue before of the offline wallet not being updated, and suggesting maybe embedding the information into an unsigned txn file to bring to the offline wallet.

This functionality has helped me with my offline wallet, and I would like to see what everyone thinks of the idea.

I am new to github, so if it is rude for me to make pull request, I am sorry. In case it can not be merged, any feedback or advice would be greatly appreciated.

Also, eventually I would like to turn this feature of mine to also update the transaction amounts and my addresses balances of my offline wallet to reflect my online watch only... but most of my attempts have failed. This is the only stable implementation I have.

Thank you for your time.