* Add samples SecondaryCommandBuffer and SeparateImageSampler.
+ made some helper functions more explicit.
* Add sample Template, some generalizations in utils, some minor improvements in various samples.
+ 12_InitFrameBuffers, 13_InitVertexBuffer, 14_InitPipeline, 15_DrawCube;
+ extend utilities and add utilities on geometries, math, and shaders
+ slightly adjust some other samples