improve performance of postgres delta_e_cie2000 query a lot, with new 'range_threshold' values - thanks to http://stackoverflow.com/a/33247813/2066849
improve performance of postgres delta_e_cie2000 query a lot, with new 'range_threshold' values - thanks to http://stackoverflow.com/a/33247813/2066849

Jaza/colorsearchtest,Jaza/colorsearchtest,Jaza/colorsearchtest