New particle system, mostly working, some small features missing.

scene/resources/default_theme/default_theme.cpp

@@ -120,7 +120,7 @@ static Ref<Texture> make_icon(T p_src) {
 }
 
 static Ref<Shader> make_shader(const char *vertex_code, const char *fragment_code, const char *lighting_code) {
-	Ref<Shader> shader = (memnew(Shader(Shader::MODE_CANVAS_ITEM)));
+	Ref<Shader> shader = (memnew(Shader()));
 	//shader->set_code(vertex_code, fragment_code, lighting_code);
 
 	return shader;