Qt5 Integration: CMake Build-System adaptions

=> Examples from QApplication to QCoreApplication to avoid QtGui and QtWidget linkage
Qt5 Integration: Build Fixes (MacOSX)

=> Build works on MacOSX 10.8.4 with Clang 4.2 (LLVM 3.2)
Merge pull request #2 from afrueh/Qt5_integration

Merged Qt5 integration