Initial version of Aperio AFI reader
Fix up subresolution population
Override openThumbBytes to prevent opening very large images
Parse wavelength, exposure, and acquisition time metadata
SVS: prevent NPE when parsing datestamps
Account for the fact that there are 3 non-pyramid images
AFI: fix thumbnail retrieval
Fix type checking tests for AFI data
Merge pull request #439 from melissalinkert/afi

Add support for Aperio AFI data