Skip arrow key processing when IntelliSense is active

I added DisplayWindowHelper to detect and skip arrow key processing when the statement completion or signature selection IntelliSense windows are active. Previously, pressing down arrow to try and select an entry from the completion window would move the caret in the text view and close the IntelliSense window.

Unfortunately, I'm still stuck on VS2012, so I cloned the .csproj and linked to the source files so I could build and run locally. I tried to preserve the VS2013 project - hopefully it still builds too. :-)