Rendertarget attachments, texture and image changes (#358)

* Add multiple color outputs for fragment shaders

* Add registers and gal enums

* Use textures for framebuffers and split color and zeta framebuffers

* Abstract texture and framebuffer targets as an image

* Share images between framebuffers and textures

* Unstub formats

* Add some formats

* Disable multiple attachments

* Cache framebuffer attachments

* Handle format types

* Add some rendertarget formats

* Code cleanup

* Fixup half float types

* Address feedback

* Disable multiple attachments in shaders

* Add A4B4G4R4 image format

* Add reversed section for image enums

Ryujinx.Graphics/Gal/GalTextureType.cs

@@ -0,0 +1,13 @@
+namespace Ryujinx.Graphics.Gal
+{
+    public enum GalTextureType
+    {
+        Snorm = 1,
+        Unorm = 2,
+        Sint = 3,
+        Uint = 4,
+        Snorm_Force_Fp16 = 5,
+        Unorm_Force_Fp16 = 6,
+        Float = 7
+    }
+}