Double mnemonic

[tadeubas]

PR to fulfill this issue: #318

• Show an asterisk after BIP39 mnemonic title if it is a double mnemonic when creating/loading a 24w mnemonic
• Option to create a new double mnemonic from camera snapshot
• Changed "Processing ..." to "Processing.." to adhere to the standard we use elsewhere
• Changed "Saving ..." to "Processing.." in order to optimize translations
• [x] Create tests...
• [x] Create docs...

What is the purpose of this pull request?

• [ ] Bug fix
• [x] New Feature
• [ ] Documentation update
• [ ] Other