feat(identity): Local importing and exporting functionality

[dariusc93]

What this PR does 📖

• Implements logic for local importing and exporting identity using mnemonic phrase
• Use ShortId in place of slice for the short id
• Split the initialization apart from creating and restoring (this will change again in the future)

Which issue(s) this PR fixes 🔨

• Relates to Restore Account, Friends, et al #43

Special notes for reviewers 🗒️

• This does not support remote exporting to another node at this time but will come later as this lays out the ground work for manual importing and exporting while internally, it may be done automatically, either at intervals or after each event.
• Exporting does not include messages at this time. This will be done separately as this interface handles the identity, friends list, requests, block list, etc.
• Does not export internal cache. This will be rebuilt after the initial exchanges when friends or users come online and push their identity to discovered peers or friends.

Additional comments 🎤

• This PR will requires the knowledge of one own mnemonic phrase prior to importing. This can be obtain prior to creating the identity, from IdentityProfile::passphrase, or from tesseract if the configuration flag is set to save it there prior to creating the identity