Fix OME-XML BinData decoding

This should fix decoding problems introduced in gh-1421, so all Bio-Formats 5.1 merge builds should turn green once this is included.  The main thing to verify is that the OMERO integration builds remain green.
If I run @snoopycrimecop's `merge/develop/latest` locally and run the tests in `OmeroJava/test/integration/ImporterTest.java` then I get errors with features like,
```
   Parameters: {message=com.google.common.io.BaseEncoding$DecodingException: Unrecognized character: >, stacktrace=java.lang.IllegalArgumentException: com.google.common.io.BaseEncoding$DecodingException: Unrecognized character: >
   	at com.google.common.io.BaseEncoding.decode(BaseEncoding.java:228)
   	at loci.formats.in.OMEXMLReader.openBytes(OMEXMLReader.java:160)
   	at loci.formats.ImageReader.openBytes(ImageReader.java:431)
```
and I wonder if this could be related to the above?