ManifestDownloader 1.8.1

• gracefully attempt a reconnection when a socket connection was closed server-side due to inactivity (main cause of this would be updating an existing installation, where minutes could pass verifying files without a single file needing to be patched)
• better handling of rare error scenarios, like an unexpected failure to send or receive data while in the middle of communication, or the ZSTD decompression failing for some reason