Since Intelli J saves the current file automatically, you don’t need to press Ctrl S.
The Runtime path to your installed Tomcat is used by Eclipse to create that Tomcat test server.
If you choose Eclipse then prepare yourself that the easiest way how to do a lot of things in Eclipse is to use command-line tools. It is much more reliable to use a command-line option. Eclipse-maven integration is not really the best one.
We have also not found a way how to import and develop mid Point in eclipse without any errors. However if it is set up correctly Eclipse should not report any fake errors in the source code. Some prefer to fight Eclipse during build, other prefer to use command-line (see below).
This page explains how to manage an App Engine project using Apache Maven, a software project management and comprehension tool.
It is capable of building WAR files for deployment into App Engine.
For more information about this new view, see Browsing and Manipulating Maven Repositories in Edition 0.6 of Developing with Eclipse and Maven.