Update "Getting Started Guides" page

-The Getting Started Guides need some serious rewriting. We can use this page: http://stage.qt-project.org/doc/qt-5.0/qtdoc/gettingstarted.html which is written in a .qdoc file.
It would then need:
-How to download and install
-how to set up Qt Creator (mention the target platform)
-link to the tutorials (the C++ and QML one)
-direct the reader where to go next (topics, examples, and so on)