Work around mono crashing on Rows.Clear()

Mono will crash if you do a Rows.Clear() and the first row isnt visible.  To
work around this, when running under mono force scroll to [0,0] cell before
issuing the Clear().

https://bugzilla.xamarin.com/show_bug.cgi?id=24372

Renamed Settings.MonoFileIO to Settings.IsUnix
Created Settings.IsMono

ROMVault2/SupportedFiles/CHD/CHD.cs

@@ -246,7 +246,7 @@ namespace ROMVault2.SupportedFiles.CHD
             _resultType = CHDManCheck.Unset;
 
             string chdExe = "chdman.exe";
-            if (Settings.MonoFileIO)
+            if (Settings.IsUnix)
                 chdExe = "chdman";
 
             string chdPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, chdExe);