Communication with Docker communicator

[pverscha]

This PR provides the foundations for communication with the local Docker daemon. We use the excellent dockerode package (https://www.npmjs.com/package/dockerode) to ease communication between the application and the Docker daemon. The following changes were made:

• Users can now select a directory in which custom databases should be stored.
• Users can set up a connection with the Docker daemon in the settings menu. The default Docker configuration settings are automatically filled in for the operating system that the user is currently using (Unix-based or Windows) and should only be changed if they did not install Docker with the default set of settings.
• A lot of statistics are shown if the connection to the Docker daemon was successful. A clear error message is displayed if no connection could be made.

Screenshots: All new configuration options, successful connection to Docker:

Unsuccessful connection to Docker:

[pverscha]

This is a list of some things that we still need to do before this PR can be finalised:

• [ ] Make sure that database selection box works (this is currently still a placeholder)
• [ ] Add some verification to the connection settings field for Docker. Right now, we already check if the contents of the field are correctly formatted according to the JSON-specification, but we should also check that no invalid fields or values or passed.