FileSaver
Description:
Creates a new FileSaver object.
 The buffer will be saved to the [class@File]'s location.
This constructor is suitable for a simple "save" operation, when the file already contains a non-null
       [property@File:location].
Parameters:
| buffer | the Buffer to save. | 
| file | the File. | 
Returns:
| a new FileSaver object. |