Show Exceptions in greater detail

[arp6333]

Thanks for the great NLogViewer, has helped me a ton. My main problem was that I wanted the ability to view Exceptions in full detail which I have done in a simple way using a popup. When an Exception / Error is logged with the exception passed with the message, for example:

catch (MyException ex) 
{ 
    logger.Error(ex, "Got exception.");
}

the NLogViewer will look the same, but the logged ListViewItem can be clicked on like so to open a popup and display the full exception:

The popup is closed using the red X or by clicking off of it. This helps debugging by displaying long and detailed errors in full.

My code also has one minor change that has the Message column wrap text so longer messages will not have to make the user scroll horizontally forever. This also allowed the Message column to fill the length of the screen when the screen is resized and gives the popup the same width as the NLogViewer. This change was to remove any unnecessary scrolling and to have the NLogViewer fit whatever width it was put into.

My examples have the LoggerName and Level columns removed but that was only because my program does not need to display them, these changes will still work with those columns in use.

[erizet]

Thank you for this PR. I think it's a great add on to the library.
But I think I found a bug when testing it. When modifyning the sample to log a exception it shows the popup correctly, but if the window is maximized the pop up only flashes for a short while at the bottom of the screen.
If you fix this bug I'll merge this PR.