container:quickstart doesn't work with annotations

[earldouglas]

Following the quick start guide in #458, tomcat:quickstart won't work. There are at least two things going wrong.

First, with nothing in src/main/webapp/, no target/webapp-quick/ directory is created, which breaks the webapp-runner command:

> tomcat:quickstart
> The specified path "target/webapp-quick" does not exist.
Usage: <main class> [options]

Second, if we manually create this directory, it seems that whatever mechanism is scanning for @WebServlet-style annotations is not finding them on the JVM classpath. Maybe it intentionally only scans the (non-existent) WEB-INF/classes/ and WEB-INF/lib/ directories.