GUI: Add recover 12 seed words option

[jeroz1]

Please add an option: Wallet > Get seed words. With optional password requirement when the wallet is encrypted.

[HyperPeek]

Without looking into the code -- is this possible? I always assumed this is a one-way just used at startup to generate the keys and reverse (from keys to seed) is not possible. May be wrong though.

[jeroz1]

I imaged this to be a GUI wrapper around getmywords in the console

[jeroz1]

The words are also printed in the dumpwallet text file.

[fdoving]

I will try to make this.

[fdoving]

I have a working implementation.
Needs some polish.