SCIFIOFormatWriter delegates canDoStacks

The canDoStacks method in SCIFIOFormatWriter now delegates to the
ome.scifio Writer's canDoStacks method. This allowed the method to be
removed from existing writers.
Converted OMEXML Reader/Writer to SCIFIO

The loci.formats OMEXMLReader and OMEXMLWriter have been unified to a
single OMEXMLFormat in ome.xml.meta. The previous OMEMetadata class has
been converted to a Metadata nested class in the new Format.

All references updated as needed.