Added metadata support in HIBs and ImageHeaders

This is a fairly uncurated patch that includes some configuration changes for my local environment alongside the new code for metadata.

To test it, run:
./runDownloader.sh downloaderinput/imagelist downloaderoutput/output.hib 4
./runDumpHIB.sh downloaderoutput/output.hib dumphib
hadoop dfs -cat dumphib/part-r-00000

You should see:
1	source_url=http://farm3.static.flickr.com/2413/1637516180_7d7aac7831_b.jpg 1024x768	(8f8e677f1235bd7e152ddbf26b35d1148df2d28)		
1	source_url=http://farm3.static.flickr.com/2386/2016921042_c351deb735_b.jpg 1024x768	(1bd35454a22c5576a3e6b691a370effc386860b8)		
1	source_url=http://farm3.static.flickr.com/2395/2016921570_5935e4cb07_b.jpg 1024x768	(98f13c755c975fa70d6f2bfbc894bc761a78486)		
1	source_url=http://farm2.static.flickr.com/1054/692713810_8bc84408c1_b.jpg 1024x768	(91dd3e8c995da64f18590ed339f7b3e3fd139e)		

This indicates that the source URL was successfully passed as meta data along with the image in the HIB file.