Doc: add "Configuring Qt Creator" to the GS page

This topic was added to the Getting Started section
in the TOC earlier, and this patch adds it also to
the page.

Change-Id: I1f310046c85ca71619d057f4710b54e8f5f5c75e
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>
Doc: modifying variable values for build and run environments

Update screenshot.

Task-number: QTCREATORBUG-13516
Change-Id: Ia2c5786f8fd7ce3f63fdc44940341f7fb3af1269
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Reviewed-by: hjk <hjk121@nokiamail.com>