Fix endianness retrieval for older OME-XML files

Introduced in adb9503; getPixelsBinDataBigEndian now returns
Pixels.BigEndian if it exists, and BinData.BigEndian otherwise.  This
prevents isLittleEndian() incorrectly returning false because
Pixels.BigEndian may be null.
Merge pull request #597 from melissalinkert/2013-06-updates

Update OME-XML population to match 2013-06 changes
Merge pull request #596 from melissalinkert/tiff-fixes

Minor defensive programming changes for TIFF-based formats
Merge pull request #600 from melissalinkert/ome-xml-equality-test

Allow a directory of OME-XML files to be specified for testEqualOMEXML
Merge pull request #601 from rleigh-dundee/dv-exposuretime

DeltavisionReader: Store exposure time in seconds, not kiloseconds
merge develop -D org -I include -E exclude: PR 528 (Tile performance improvements for VMS and NDPI)
merge develop -D org -I include -E exclude: PR 556 (Add ``mkfake`` tool)