[FOR REVIEW ONLY] Update "File > Open Folder..." dialog with Windows' Open File dialog in pick folders mode.

While investigating 'brackets' issue https://github.com/adobe/brackets/issues/889, which was opened in lieu of 'brackets-app' issue https://github.com/adobe/brackets-app/issues/120, I noticed that (in the latter issue's discussion) NJ suggested looking at newer implementations of the Windows common file dialogs to solve the double-click issue.  Unfortunately, it appears that dbl-click, even in the newer implementation, is still not the Microsoft-supported/recommended way of selecting and confirming the dialog.  However, here's code to update the dialog, in case we're interested.

This Pull Request replaces the code implementing Brackets' feature "File > Open Folder..." currently using SHBrowseForFolder() with the MSDN-recommended implementation using IFileDialog + FOS_PICFOLDERS.

More specifically, as suggested by MSDN (http://msdn.microsoft.com/en-us/library/windows/desktop/bb762115%28v=vs.85%29.aspx), for Vista and later OSes, apps should use the newer Open File dialog in pick folders mode.

The only "downside" to pulling this new code (so far as I can tell) is that the selected folder is remembered for the next time that the dialog appears, which might interfere with the "Please select the Brackets index.html file" dialog in development builds.