Review WebServers' auto-start behavior

Auto-start was introduced before 1.0. The intent appears to have been to prevent the server from starting. At the time it was when the port was set to 0. It's now when the port is set to a negative value. ServletContextAware is also mentioned which suggests that such components should still be called with the current ServletContext.

I think the name autoStart is misleading. It doesn't control whether the web server will be started automatically, but what start will do. Put another way, calling start() on a web server with auto-start disabled does not put it in the same state as one that was created with auto-start enabled.

We have four web servers now, and various behaviors when auto-start is disabled:

With the opportunity that 4.0 provides for breaking changes, we should review the auto-start behavior. Given the inconsistency of the current implementations we should consider if the feature's needed at all. It also doesn't appear to be documented so it perhaps isn't widely used. If we want to keep it, we should, if possible, offer consistent behavior across all web servers. We should also consider renaming it.

Start by comparing the auto-start handling in NettyWebServer, JettyWebServer, TomcatWebServer, and UndertowWebServer. Review the linked introduction commit and current behavior for disabled auto-start, then determine whether the feature should remain and what consistent behavior or renaming is required. Done means the project has a decided, consistent approach across the web servers.