Minor fixes/features

[cal-overflow]

• Build Script: change from having to type "default" to just leaving blank will result in default environment variable values
• Ability to update motion detection threshold through frontend (flask website)

Client-Server Relationship:

• Ensure that server recognizes when client has disconnected. The server does not always acknowledge the connection closing
• Ensure that clients are always able to automatically re-connect to server in the event the server crashes/restarts

[cal-overflow]

• If the camera feed was recording when the client disconnected, have the server save the footage before closing the clients' process