Rename BIP39 Seed field

[andrewkozlik]

I propose to rename two fields in the BIP39 tool. The reason why I stumbled upon this is I realized it's not obvious how to use the master secret from iancoleman.io/slip39 in the BIP39 tool.

BIP39 Seed
This is indeed the correct terminology, but it can be pretty confusing, considering that the mnemonic is often colloquially referred to as "recovery seed" or "seed". The BIP39 spec also uses the term "binary seed", which IMHO is slightly clearer. Furthermore, this field can also be used for the SLIP39 master secret, and what it in fact represents is the BIP32 seed byte sequence, which is also referred to as the "seed value", "master seed", or just "seed" in BIP32. Unfortunately some of these specs fail to use a consistent naming and what's more, even the terminology used by people in the field is often different. I propose that the name of this field be changed to any of the following. Ideally pick one and add a tooltip text with all the other alternatives:

• BIP39 binary seed
• BIP32 seed byte sequence
• BIP32 master seed
• SLIP39 master secret

BIP32 Root Key
The term "root key" is not actually used in BIP32. I propose one of the terms used in BIP32:

• master extended private key
• master extended key
• (serialized) master node

Links:
https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
https://github.com/satoshilabs/slips/blob/master/slip-0039.md