Merge glTF scene rendering sample (#744)

* Started reworking the scene rendering to sample
Use glTF instead of ASSIMP, per-material pipelines, material loading, etc.

* Visibility toggle for scene nodes

* Fixed lighting, updated GLSL and HLSL shaders

* Renamed sample

* Code-Cleanup, comments, validation fixes

* Android build

* Started on tutorial for glTF scene rendering sample

* Minor code cleanup

* Adding new chapters to the tutorial for glTF scene rendering sample

* Added info on normal map shader bindings, spelling

* Added drawing chapter

* Getter for texture descriptors

Makes code a easier to read

* Renamed glTF scene sample

* Add markdown files to projects

* Updated readme, separate chapter for glTF samples

* Comments

* Removed unused screenshot

data/shaders/glsl/gltfloading/mesh.vert

@@ -0,0 +1,37 @@
+#version 450
+
+layout (location = 0) in vec3 inPos;
+layout (location = 1) in vec3 inNormal;
+layout (location = 2) in vec2 inUV;
+layout (location = 3) in vec3 inColor;
+
+layout (set = 0, binding = 0) uniform UBOScene
+{
+	mat4 projection;
+	mat4 view;
+	vec4 lightPos;
+} uboScene;
+
+layout(push_constant) uniform PushConsts {
+	mat4 model;
+} primitive;
+
+layout (location = 0) out vec3 outNormal;
+layout (location = 1) out vec3 outColor;
+layout (location = 2) out vec2 outUV;
+layout (location = 3) out vec3 outViewVec;
+layout (location = 4) out vec3 outLightVec;
+
+void main() 
+{
+	outNormal = inNormal;
+	outColor = inColor;
+	outUV = inUV;
+	gl_Position = uboScene.projection * uboScene.view * primitive.model * vec4(inPos.xyz, 1.0);
+	
+	vec4 pos = uboScene.view * vec4(inPos, 1.0);
+	outNormal = mat3(uboScene.view) * inNormal;
+	vec3 lPos = mat3(uboScene.view) * uboScene.lightPos.xyz;
+	outLightVec = lPos - pos.xyz;
+	outViewVec = -pos.xyz;		
+}