Fix bug where previously-deleted contacts are re-added to left pane on contact import (#1811)
Fix bug where the main window would be created off-screen, inaccessible (#1830)
Fix issue where certain sync messages to iOS would result in a new message alert (#1843 and #1857)
Key rotation updates (#1833 and #1846):
- Save prekeys optimistically after generation, even if upload appears to fail
- Track confirmations from server in prekey
- New prekey cleanup behavior: favoring confirmed keys, but always keeping three
- Log all failures resulting from signed prekey rotation
- Retry rotation if we run into a failure
- Force rotation when starting up new version, to fix Chrome interference (https://github.com/WhisperSystems/Signal-Desktop/releases/tag/v0.44.13)
Dev: