title: find_package Config file with components
body: <p>i have a cmake package with a Config file supporting components, e.g. </p>
  
  <pre><code>find_package(myPack REQUIRED COMPONENTS foo bar)
  </code></pre>
  
  <p>in myPackConfig.cmake I typically do</p>
  
  <pre><code>foreach(comp ${myPack_FIND_COMPONENTS})
      if(TARGET myPack::${comp})
           find_package(${comp})
      endif()
  endif()
  </code></pre>
  
  <p>i.e. loop all components and find them. But is it possible to include ALL components if none is given? E.g. when doing</p>
  
  <pre><code>find_package(myPack)
  </code></pre>
  
  <p>I want to have ALL components (foo, bar, baz et.c.)</p>
  
  <p>thanks</p>