Сan't distinguish click and panning event about cyotek.windows.forms.imagebox

[snechaev]

I hit the same problem.
In my case the IsPanning is always true inside a click handler so it is impossible to distinguish between "click" and "drag to pan" actions.

A quick research shown that a problem was introduced into rev. 3aa026b (Added PanMode and AllowFreePan properties). In this revision the ProcessPanning is called directly from OnMouseDown handler (so, before the click event) and when click event happens, the pan is already started and IsPanning=true.

Cyotek.Windows.Forms.ImageBox/Cyotek.Windows.Forms.ImageBox/ImageBox.cs

Lines 4018 to 4030 in 2fb350f

	if (e.Button != MouseButtons.None)
	{
	if (_panStyle == ImageBoxPanStyle.Free)
	{
	// already panning, abort
	this.ProcessPanEvents(ImageBoxPanStyle.None);
	}
	else
	{
	_mouseDownStart = NativeMethods.GetTickCount();
	this.ProcessPanning(e);
	}
	}

It looks like this can be fixed just by adding additional checks for AllowFreePan and mouse button and then call ProcessPanning only if Free Pan is enabled and the button is middle button.

I will provide a pull request with the fix, but I'm unsure that such a fix will play good with all the features and modes of ImageBox.