Made Keyframe objects thread safe, by generating the values as Points are added, and the Timeline's Open and Close logic was made thread safe, so a reader is not closed while it's still being accessed on another thread. Also removed some unneeded code and comments.

src/KeyFrame.cpp

@@ -62,6 +62,10 @@ void Keyframe::AddPoint(Point p) {
 
 	// Set Handles (used for smooth curves).
 	SetHandles(p);
+
+	// Check if it needs to be processed
+	if (needs_update)
+		Process();
 }
 
 // Add a new point on the key-frame, with some defaults set (BEZIER, AUTO Handles, etc...)