[#1363] Binary address book serialization

[LukasKorba]

Closes #1363

• Local storage for address book is now primary source of data
• Remote storage for address book is used as a backup, syncing is prepared and merge strategy is WIP
• The data serialization/deserialization is prepared, no encryption in place
• The data are versioned and checked
• lastUpdated data are stored as well
• Keychain stores a struct for encryption, in case there is more than just 1 key

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