Updated ImageNet Tutorial to reflect new merged train+val prototxt format. Also corrected 4,500,000 iterations  -> 450,000 iterations.
Tried to clarify function of `include' lines and train vs. test network differences
Merge pull request #923 from yosinski/doc-update

ImageNet tutorial update to merged train_val.prototext
Added Eltwise absolute value operation, usefull for implementation of siamese networks\!
Added the MKL alternative for Abs
Removed the old implementation of fabs to replace it with MKL/non-MKL/GPU abs operation
Added Eltwise absolute value operation, usefull for implementation of siamese networks\!
Added the AbsVal Layer, replaced the default fabs
Fixed the the style
Revert the changes in test_eltwise and vision_layer