Support for Qt5
This adds support for Qt5 using both qmake and CMake.
It should be noted that glew can conflict with QOpenGLFunctions, which is automatically included by this:
#include <QtGui>
So instead, when using glew, all Qt classes should be included individually as needed.
I tested with Qt 4.8 and Qt 5.8.
When using CMake, by default, Qt5 is used. If it cannot be found, it falls back to Qt4. If Qt4 should be explicitly used, this can be specified by setting MET3D_FORCE_QT4 like this: cmake (...) -DMET3D_FORCE_QT4=ON