Reimplemented Renderer2D

- Renderer2D now static
- Renderer now calls Init and Deinit of Renderer2D
- Renderer2D  now calls Init and Deinit of FontRenderer
- Fixed Deinit order of Layers and renderer (e.g. Layers now deinit first)
- Sandbox2D now uses SandboxApp (only loads different layer)

Sandbox/content/Shaders/spritebatch.hlsl

@@ -0,0 +1,41 @@
+Texture2D Texture : register(t0);
+SamplerState Sampler : register(s0);
+
+cbuffer Constants : register(b0)
+{
+    float4x4 ViewProjection;
+};
+
+struct VS_Input
+{
+    float2 Position     : POSITION;
+    float2 Texcoord     : TEXCOORD0;
+    float4x4 Transform  : TRANSFORM;
+    float4 Color        : COLOR;
+    float4 UVTransform  : TEXCOORD1;
+};
+
+struct PS_Input
+{
+    float4 Position : SV_Position;
+    float2 Texcoord : TEXCOORD;
+    float4 Color    : COLOR;
+};
+
+PS_Input VS(VS_Input input)
+{
+    PS_Input output;
+
+    output.Position = mul(ViewProjection, mul(input.Transform, float4(input.Position, 0.0f, 1.0f)));
+    output.Texcoord = input.UVTransform.xy + input.UVTransform.zw * input.Texcoord;
+    output.Color = input.Color;
+
+    return output;
+}
+
+float4 PS(PS_Input input) : SV_Target0
+{
+    return Texture.Sample(Sampler, input.Texcoord) * input.Color;
+}
+
+#effect[VS=VS, PS=PS]