Trim docker image size

[rhythnic]

• Use alpine version of node image
• Use --production flag on npm install
• Ensure LPWAN Server on alpine image passes test suite

[rhythnic]

Was unable to use alpine because of dependency on ttn package. The package is used because there's no TTN v2 API for creating an HTTP integration, though it can be done manually. The package is used to subscribe to events from TTN to accomplish an integration. We should probably remove that package and ask the user to manually add an http integration.