Merge "docs: Added usability study link to sdk DL" into mnc-docs

  <li><a href="#Requirements">System Requirements</a></li>

  <li><a href="#Other">Other Download Options</a></li>

  <li><a href="{@docRoot}sdk/installing/migrate.html">Migrating to Android Studio</a></li>

  <li><a href="https://www.google.com/intl/en/usability/index.html?l=9&reserved=0&pType=devel&productTag=0&campaignType=ghc&campaignDate=0&labelTag=0&referral_code=ASDWNLD">Participate in usability research</a></li>

  <li><a href="https://docs.google.com/a/google.com/forms/d/1mjsyfzv3HAnDY-_Kfj-3QJKdpuksyMFs9e73CRwmT6Q/viewform"

target="_blank">Take a Survey</a></li>

</ul>