Clean up and document IIIFInfo parser
Clean up and document IIIFInfo parser

Optional preferred options are now reduced to the two options that
depend on the image service's supported features: format and quality.

stweil/ol3,stweil/ol3,geekdenz/openlayers,ahocevar/ol3,geekdenz/openlayers,openlayers/openlayers,stweil/openlayers,ahocevar/openlayers,geekdenz/openlayers,stweil/openlayers,oterral/ol3,geekdenz/ol3,ahocevar/ol3,ahocevar/openlayers,oterral/ol3,tschaub/ol3,ahocevar/ol3,stweil/ol3,stweil/openlayers,bjornharrtell/ol3,openlayers/openlayers,adube/ol3,ahocevar/openlayers,bjornharrtell/ol3,ahocevar/ol3,bjornharrtell/ol3,geekdenz/ol3,tschaub/ol3,geekdenz/ol3,geekdenz/ol3,stweil/ol3,tschaub/ol3,oterral/ol3,openlayers/openlayers,adube/ol3,tschaub/ol3,adube/ol3