Added VlFeat SIFT detector (because it is available in the old VLFeat version).
Added VlFeat SIFT detector (because it is available in the old VLFeat version).

vlfeat/vlbenchmarks,vlfeat/vlbenchmarks,CVML/vlbenchmarks,andersbll/vlbenchmarks,CVML/vlbenchmarks,andersbll/vlbenchmarks,andersbll/vlbenchmarks,CVML/vlbenchmarks,andersbll/vlbenchmarks,vlfeat/vlbenchmarks