Implement Support For Project Encryption

[rjra2611]

• Add lean encrypt / lean decrypt commands: Encrypt / Decrypt files on disk
• Update lean cloud pull
  • Add --encrypt flag: encrypt files from the cloud (if required) in memory and write to disk, update local project's encryption state
  • Add --decrypt flag: decrypt files from the cloud (if required) in memory and write to disk, update local project's encryption state
• Update lean cloud push
  • Add --encrypt flag: encrypt local files (if required) in memory and push to cloud, update cloud project's encryption state
  • Add --decrypt flag: decrypt local files (if required) in memory and push to cloud, update cloud project's encryption state
• Add Tests
• Closes https://github.com/QuantConnect/lean-cli/issues/368