RFC_0014: DUBP Mnemonic

added 8 commits

• a4a69cc0...1a1adf15 - 2 commits from branch master
• c18865f7 - [MNEMONIC] create RFC_0014_Dubp_Mnemonic
• 94a6d14f - [MNEMONIC] add pubkey to example
• 70e7916a - [MNEMONIC] add param dklen & remove some french paragraph
• 82467172 - [MNEMONIC] salt: base16 is only a human representation
• 7ee911c8 - [MNEMONIC] remove entropy suggestions for DEWIF code
• 1078ec2f - [MNEMONIC] Fix typo, English

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