Fix and Improve initial Setup of QtCreator

In a C++ Course we had several students with no Qt or C++ environment installed and experienced some bugs and other issues that should be fixed.

I provided the Windows SDK (latest) and QtCreator (2.0.1). This was confusing for the students, but since I know that they will keep the installed environment for years (Qt could integrate an auto updater...) I wanted them to have a version with less bugs.

The problems started afterwards. Neither of the programs puts an information into the system path. That means that one has to add a Qt environment
manually in Creator. This is a complete uncommon behavior for windows programs. The installer should set up the inital environment correct. Just for your information: None of the students understood which path to add and it we had to check almost every students settings to get their editor working.

After we started writing code we had the problem (this is a real bug) that in most cases QtCreator did not compile anything but instead printed a message about make not found or similar. We first thought that the path (see above) would be wrong, but that was not the problem. Instead nothing was set up wrong. We had to restart QtCreator to get it working.

The third problem was that in my example project all students could not link the executable because it failed to link the project relative path libraries. Why ? Because of
shadow builds. I had told all students to switch it off, but most did not and it took me some time to find the (non existent error in the pro file), just to find out that it is related to shadow builds. Again here no one understood why QtCreator is initially set up such, that it breaks projects from building.

Summary:

• provide path and set up Qt Environment on installation
• fix settings of mingw dir
• disable auto shadow builds