CB-6994 - Windows 8 does not save big file transferred using Blob

When trying to save Blob using FileWriter.write method, if the blob's size is too high, we get a stack overflow exception during the conversion of the blob into an basic array.

In order to avoid this exception, we pass the Blob or File directly in FileProxy (avoid the conversion to ArrayBuffer) and we use a specific method in FileProxy to save the Blob directly to the filesystem by using Streams (safe).

More info at : https://issues.apache.org/jira/browse/CB-6994
1. in case of data is File it fails since File does not have msDetachStream method
2. I would also do (detachStream || msDetachStream) so that it will work in future versions