[WIP] Reliability improvements

[hulthe]

• Fix AsyncDrop hanging when modem restarts
• Fix AsyncDrop clean up logic
• Add timeouts to all AT commands
• Add timeouts to modem power
• Add timeouts to TCP connect
• Clean up connection if TCP connect errors
• Use non-blocking channels to send ConnectionMessages
• Improve handling of unexpected ConnectionMessages
• Add timeouts to waiting for registration
• Purge windows line endings
• Make line reader only look for \n instead of \r\n (voltage warnings only ends with \n)
• Add more docs
• Other stuff