Remove unnecessary uses of "takeScreenshot" (#349)

orx-time-operators/src/demo/kotlin/DemoEnvelope.kt

@@ -11,11 +11,6 @@ fun main() {
             val size = Envelope(50.0, 400.0, 0.5, 0.5)
             val rotation = Envelope(easingFactor = 0.4)
 
-            if (System.getProperty("takeScreenshot") == "true") {
-                extend(SingleScreenshot()) {
-                    this.outputFile = System.getProperty("screenshotPath")
-                }
-            }
             extend(TimeOperators()) {
                 track(size, rotation)
             }

orx-time-operators/src/demo/kotlin/DemoLFO.kt

@@ -12,9 +12,8 @@ fun main() {
             val size = LFO()
             val rotation = LFO(LFOWave.Sine)
             if (System.getProperty("takeScreenshot") == "true") {
-                extend(SingleScreenshot()) {
-                    this.delayFrames = 10
-                    this.outputFile = System.getProperty("screenshotPath")
+                extensions.filterIsInstance<SingleScreenshot>().forEach {
+                    it.delayFrames = 10
                 }
             }
             extend(TimeOperators()) {