Minor refactor of built-in QSGVideoNodes.

- Load shader source from resource files.
- Correctly report material types: each material can use different
  shaders depending on the video pixel format but it was reporting
  a unique material type. This was causing the node to keep using
  the same shader even if its pixel format changed.

Change-Id: Ib903ecd6e7dd1dd56d7cefe255ab7049933df17d
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

src/qtmultimediaquicktools/qtmultimediaquicktools.pro

@@ -32,3 +32,17 @@ HEADERS += \
     qsgvideonode_yuv.h \
     qsgvideonode_rgb.h \
     qsgvideonode_texture.h
+
+RESOURCES += \
+    qtmultimediaquicktools.qrc
+
+OTHER_FILES += \
+    shaders/rgbvideo.vert \
+    shaders/rgbvideo_padded.vert \
+    shaders/rgbvideo.frag \
+    shaders/rgbvideo_swizzle.frag \
+    shaders/biplanaryuvvideo.vert \
+    shaders/biplanaryuvvideo.frag \
+    shaders/biplanaryuvvideo_swizzle.frag \
+    shaders/triplanaryuvvideo.vert \
+    shaders/triplanaryuvvideo.frag