--User changes

-Attempt to preserve xaos when adding xforms. Note this is not an exact copy, but just a preservation of some values based on position.
 -Add some acceleration to the changing of spinner values when dragging the right mouse button to adjust.
 -Make the pivot be the center of the viewable area when doing drag/rotate/scale with the right mouse button.
 --Clamp minimum scale to 10
 --Draw a line from the mouse position to the pivot.
 -Keep a cache of the last added final xform with each flame so that it can be quickly added, removed, then added back for testing its effect.
 --This is not saved with the xml file and is solely for interactive editing.

--Bug fixes
 -File filtering in open and save dialogs were broken.
 -Right clicking on integer spin boxes was causing the context menu to pop up, when it should be supressed just like double spin boxes.
 -Deleting xforms was still broken.

--Code changes
 -Refactor the code for adding and pasting xforms into a single global static function called AddXformsWithXaos().

Source/Fractorium/DoubleSpinBox.cpp

@@ -146,6 +146,7 @@ void DoubleSpinBox::OnTimeout()
 	int xdistance = m_MouseMovePoint.x() - m_MouseDownPoint.x();
 	int ydistance = m_MouseMovePoint.y() - m_MouseDownPoint.y();
 	int distance = abs(xdistance) > abs(ydistance) ? xdistance : ydistance;
+	distance = Sqr(distance) * (distance < 0 ? -1 : 1);
 	double scale, val;
 	double d = value();
 	bool shift = QGuiApplication::keyboardModifiers().testFlag(Qt::ShiftModifier);