save from python for net surgery

0. Scheme desired parameters.
1. Do surgery on the net through `net.params['name'][idx].data[...] = `.
2. Save post-operation net params by `net.save('fname')`.

Handwoven deep nets, anyone?
define fully-convolutional imagenet model
make notebook for net surgery of fully-convolutional model
Merge pull request #455 from shelhamer/pycaffe-save

Save from python for net surgery
add net surgery link to docs (+ drop old comment)
Merge pull request #495 from jeffdonahue/refactor-net

Minor Net::Init refactoring: name loop indices, add helpers
change Backward interface: propagate_down is a vector -- use to fix
long-standing issue with how this is handled in loss layers (esp.
EuclideanLossLayer)