[Qt-creator] Real shadow builds with CMake and Qt Creator 2.6

[Peter Kümmel]

Currently Qt Creator "pollutes" the source directory with a CMakeLists.txt.user
file even when building out-of-source (shadow).

A patch and Windows binary which adds a option in the CMake wizard dialog
to also save the .user file in the build directory could be found here:

https://github.com/syntheticpp/qt-creator
     (branch 2.6-cmake-shadow-user-file, based on the 2.6 branch)
https://github.com/syntheticpp/qt-creator/downloads

A <procject name>.qtcreator file will be created in the build directory
which should be opened instead of the original CMakeLists.txt file.

After associating .qtcreator with qtcreator.exe also opening the
project with a double click is possible.
When on Windows the association doesn't work removing the registry key
    [HKEY_CURRENT_USER\Software\Classes\Applications\qtcreator.exe
and selecting the Qt Creator exe again helps.

Peter