Added addalpha techniques for particle effects, where the texture or vertex color alpha should modulate the addition strength. Closes #349.

Bin/CoreData/Techniques/DiffAddAlpha.xml

@@ -0,0 +1,3 @@
+<technique vs="Unlit" ps="Unlit" psdefines="DIFFMAP">
+    <pass name="alpha" depthwrite="false" blend="addalpha" />
+</technique>

Bin/CoreData/Techniques/DiffVColAddAlpha.xml

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+<technique vs="Unlit" ps="Unlit" vsdefines="VERTEXCOLOR" psdefines="DIFFMAP VERTEXCOLOR">
+    <pass name="alpha" depthwrite="false" blend="addalpha" />
+</technique>

Bin/CoreData/Techniques/NoTextureAddAlpha.xml

@@ -0,0 +1,3 @@
+<technique vs="Unlit" ps="Unlit">
+    <pass name="alpha" depthwrite="false" blend="addalpha" />
+</technique>

Bin/CoreData/Techniques/NoTextureVColAddAlpha.xml

@@ -0,0 +1,3 @@
+<technique vs="Unlit" ps="Unlit" vsdefines="VERTEXCOLOR" psdefines="VERTEXCOLOR">
+    <pass name="alpha" depthwrite="false" blend="addalpha" />
+</technique>