Refactored the SignalApp class to Swift
Fixed a horizontal alignment issue in the ConversationTitleView
Fixed an issue where expiration timer update messages weren't migrated or rendering correctly
Fixed an issue where expiring messages weren't migrated correctly
Fixed an issue where closed groups which had been left were causing migration failures (due to data incorrectly being assumed to be required)
Shifted the Legacy Attachment types into the 'SMKLegacy' namespace
Moved all of the NSCoding logic for the TSMessage
Added migrations for contacts and started working through thread migration (have contact and closed group threads migrating)
Deprecated usage of ECKeyPair in the migrations (want to be able to remove Curve25519Kit in the future)
Updated the migrations so they can specify whether a configuration sync is required
Moved the config sync logic into a MessageSender extension (makes far more sense than AppDelegate)
Fixed a bug where the ShareVC was triggering the 'versionMigrationsDidComplete' twice
Removed a couple of imports for files that had been deleted