You should only need to define the project with jar packaging (and as it is the default you don't need to declare it).
If you define the application-client.xml in the src/main/resources/META-INF folder it will be included in the META-INF folder of the final jar.
To define additional information you need to configure the jar plugin as below.
<project>
...
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>2.2</version>
<configuration>
<archive>
<manifest>
<mainClass>com.mycompany.app.App</mainClass>
<addClasspath>true</addClasspath>
</manifest>
<manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>
</archive>
</configuration>
</plugin>
</plugins>
</build>
...
</project>
Check out the guide to working with manifests for full details