Fix to properly decode Unicode in Android

I was unable to properly read wkt files on Android. The fix was to check if text actually come in pair of bytes.
I found this on codeplex, but I don't think it ever went into the main codebase.

To successfully read the wkt file to a string in Android I had to do this
````
var wktProj = File.ReadAllText(Path.ChangeExtension(shapeFileName, "prj"), Encoding.UTF8);
````
Using Unicode here produced wrong results.

Then 
````
   var pcs = CoordinateSystemWktReader.Parse(ww) as ICoordinateSystem;
````
to get the project would fail.