Large refactor of Timeline, TimelineBase, ClipBase, and Clip, to allow a Clip access to the parent timeline instance (if available), and thus, certain properties (preview size, timeline FPS, etc...). This allows for a simpler rendering of Clip keyframes (during the Clip::GetFrame method), and a simpler Timeline class, that can change the preview window size dynamically and no longer requires a Singleton Settings class.

- Also removed "crop" from Clip class, as it was never implmeneted correctly, and we have a fully functional "crop" effect when needed
 - Added caching to Clip class, to optimize previewing of cached frames (much faster than previous)

src/EffectBase.cpp

@@ -138,3 +138,13 @@ Json::Value EffectBase::JsonInfo() const {
 	// return JsonValue
 	return root;
 }
+
+/// Parent clip object of this reader (which can be unparented and NULL)
+openshot::ClipBase* EffectBase::ParentClip() {
+	return clip;
+}
+
+/// Set parent clip object of this reader
+void EffectBase::ParentClip(openshot::ClipBase* new_clip) {
+	clip = new_clip;
+}