Let's make Sealious focus on being a good ORM, first and foremost. With that in mind, we can move the responsibility of creating and starting a koa server to sealious-playground.

app.start() should no longer start a web server, and all http-server config should be removed from the Config type.

Equivalent functionality has to be moved to Sealious Playground.

Sealious should only use koa for tests, and it should be a devDependency instead of a regular dependency.