Feature/point cloud rendering

[RedImp1470]

Adds the first version of point cloud rendering, see the examples "PointCloudOutOfCore" and "PointCloudLive"

• Performance improvements by using int keys for the shader parameter dictionaries in RenderContext
• Reworking of MeshFromPointList
• Reworking of RenderSet.Delta
• Correctly dispose of Texture and WritableTexture
• Made Managers, FontImp and RenderContext disposable
• Deleted VAO when the Mesh is disposed
• Out of Core loading example: reworked multithreading and OpenGL/GLFW context handling in Fusee
• Enhanced PointCloudSurfaceEffect
  • Added ColorMode
  • Added EDL