ENABLE_3DCONNEXION_DEVICES - 1st installment of support for 3Dconnexion devices

Implemented using hidapi library (https://github.com/libusb/hidapi) and https://github.com/koenieee/CrossplatformSpacemouseDriver/tree/master/SpaceMouseDriver as reference

Unsolved issues:

- When manipulating the SpaceNavigator wxWidgets generates a mouse wheel event that needs to be filtered out

- wxWidgets does not detect devices being connected/disconnected to the pc

- Current state forces a continuous rendering

- Current state misses dependence on camera zoom

- Non intuitive movement limits

- Translation and rotation speed factors are hardcoded

- Number of device buttons hardcoded

src/slic3r/GUI/GLCanvas3D.hpp

@@ -486,6 +486,9 @@ public:
     void set_color_by(const std::string& value);
 
     const Camera& get_camera() const { return m_camera; }
+#if ENABLE_3DCONNEXION_DEVICES
+    Camera& get_camera() { return m_camera; }
+#endif // ENABLE_3DCONNEXION_DEVICES
 
     BoundingBoxf3 volumes_bounding_box() const;
     BoundingBoxf3 scene_bounding_box() const;