Add an axis aligned box in the geometry module.

Some naming questions:
- for "extend" we could also think of: "expand", "union", "add"
- same for "clamp": "crop", "intersect"
- same for "contains": "isInside", "intersect"
=> ah "intersect" is conflicting, so that eliminates this one !

Eigen/Geometry

@@ -33,6 +33,7 @@ namespace Eigen {
 #include "src/Geometry/Scaling.h"
 #include "src/Geometry/Hyperplane.h"
 #include "src/Geometry/ParametrizedLine.h"
+#include "src/Geometry/AlignedBox.h"
 
 } // namespace Eigen