Support other BIP39 seed / BIP39 Mnemonic words length

[nifri]

Current Behaviour

The Lethekit seedtool will operate as only option with 128 bit BIP39 seed / 12 word BIP39 Mnemonic length.

Proposed Change

Allow a user to select the BIP39 seed length BIP39 Mnemonic word length. This option could for example be located in the first "No Seed" screen as a new option "Seed Length".

After selecting a seed length all following calculations should be performed with the selected seed length.

If the user makes no choice a default (for example 128 Bit) could be applied.