Provide config in login-style interaction

[tvdhout]

Currently, we require a config file with credentials for ddosdb to be passed each time running the dissector. It would be nicer if the user can provide those details once in a docker login-type fashion. An interactive prompt asking for ddosdb hostname and API key. The credentials would be saved locally.

If the dissector would be deployed as package, the login can be saved in the interpreter's share directory.