title: Coverage metrics do not consider code without tests?
body: <p>In a project where some components have test coverage and others don't it seems that SonarQube only calculates the total code coverage based on the components that have coverage. I would expect that the lines of code in components without test coverage are classified (at least for calculations) as having 0% code coverage.</p>
  
  <p><strong>Example:</strong></p>
  
  <ul>
  <li>Project X
  
  <ul>
  <li>Module 1: 100% coverage</li>
  <li>Module 2: N/A coverage (I reason that this is equivalent to 0% in a computation!)</li>
  </ul></li>
  </ul>
  
  <p>SonarQube coverage (Project X): 100%</p>
  
  <p><strong>How is the total coverage calculated? If this is by design, why?</strong></p>