title: MavenProject setValue not change pom.xml
body: <p>I have a problem with MavenProject class. I make a maven plugin and i am using this class to get pom properties like groupId and version. Everytime when i use my plugin to set something- e.g:</p>
  
  <pre><code>public class versionGoal extends AbstractMojo {
  
  /**
   * @parameter default-value="${project}"
   */
  private MavenProject mavenProject;
  
  /**
   * @throws org.apache.maven.plugin.MojoExecutionException
   */
  public void execute() throws MojoExecutionException
  {
      this.mavenProject.setVersion("9.0.0");
  }
  </code></pre>
  
  <p>}</p>
  
  <p>after execution e.g in test phase nothing change. But if i try add in code line: mavenProject.getVersion() after line this.mavenProject.setVersion("9.0.0") return me "9.0.0", but pom.xml wouldn't be changed. </p>
  
  <p>Probably it's some stupid mistake, i know:) And i know that exist version-maven-plugin, but i don't want to use it.</p>
  
  <p>Thanks for help!</p>