Document Manager; Files page now uses WebView to display file contents

The "Files" page shown on Account, Client etc forms now uses the WebView control to preview file contents.

The main advantage is simplifying the underlying technologies and supporting PDF files.

Note, CSV and TIFF files are no longer supported in the file preview.

To view CSV and TIFF files, and for that matter any file, e.g. a Word Document, you can still drilldown to open the file.