Returns the path name relative to the project folder where the asset is stored.
全てのパスはプロジェクトフォルダに対する相対指定とします。例えば "Assets/MyTextures/hello.png" です。
	@MenuItem("GameObject/Create Material")
	static function CreateMaterial () {
		// Create a simple material asset
		var material = new Material (Shader.Find("Specular"));
		AssetDatabase.CreateAsset(material, "Assets/MyMaterial.mat");
		// Print the path of the created asset
		Debug.Log(AssetDatabase.GetAssetPath(material));
	}