- load OBJ file
- set offscreen rendering
- set roll angle of the camera
- get Mat screenshot of the current scene
- remove all lights from the scene
- add a custom light in the scene
- modify the size of the WImage3D widget
- added ambient property for the widget

Changed Vec3d in cv::viz::Color

Renamed method getMatScreenshotin getScreenshot

Modified showWidget

Fixed on viz::Color and reverted fix on vtkProp3D

Removed cameraRoll method

Merged load mesh method (for ply and obj file)

Fixed doc

Fixed cv::viz::WImage3D::setSize for vtk5.8

Fixed enum for cv::viz::Mesh::load

merged background color with background gradient methods, updated tests to show description of scene

moved some headers to precomp.hpp

fixes based on the feedback: window name prefix is automatically added when it is not there, singleton class returns reference instead of pointer, destructor is private, release function implemented

initial shared pointer implementation for Viz3d, singleton VizAccessor, cv::viz::get function initial implementation

initial implementation of projection matrix, 3D to window coordinates, window coordinates to 3D ray (not yet tested)