title: cmake - support of Visual Studio filters
body: <p>I have a cmake file that generate a solution with several sub projects, but I wish a "filter" (VS specific feature) to group all my thirdparty libraries together.</p>
  
  <p>An example, for now I use the ZLIB library, it appear as a project, I use the following:</p>
  
  <pre><code>add_subdirectory(zlib)
  </code></pre>
  
  <p>To add such filter, I have try the following :</p>
  
  <pre><code>add_subdirectory(zlib)
  FILE(GLOB_RECURSE ZLIB_SOURCE "zlib/*")
  SOURCE_GROUP("THIRDPARTY" FILES ${ZLIB_SOURCE})
  </code></pre>
  
  <p>In this example I wish to put the "zlib" project into a "THIRDPARTY" filter.</p>
  
  <p>But nothing is changed in my solution ! I use VS2017 and cmake 3.8</p>
  
  <p>Any idea ?</p>