OpenMesh 8.0 release

This release now relies on compilers supporting C++11 or higher. Therefore Visual Studio 2013 is no longer supported.

The major upgrade in this release is the integration of an Eigen3 wrapper providing a direct replacement of the integrated vector type (Vec3d/Vec4d). You can now use Eigen3 vectors as the basic data type inside OpenMesh.

We also improved several readers and writers. Furthermore the new SmartTagger class has been added which can be used to tag primitives in the mesh while providing an O(1) reset of the tagging.

Next to this, we removed the glut requirement from the apps.