Add Net HasBlob GetBlob HasLayer GetLayerByName to simplify feature extraction

Conflicts:

	include/caffe/net.hpp
	src/caffe/net.cpp
Add __builtin_popcount* based fast Hamming distance math function
Add image retrieval example
Add feature extraction example
Add feature binarization example
Simplify image retrieval example to use binary features directly
Fix bugs in the feature extraction example
Enhance help, log message & format of the feature extraction example
Fix bugs of the feature binarization example
Fix bugs in the image retrieval example
Fix saving real valued feature bug in the feature extraction example
Change feature binarization threshold to be the mean of all the values
 rather than zero in the feature binarization example
No print
Save and load data correctly in feat extracion, binarization and IR demo