use /usr instead of /usr/local for default Python include/lib

This makes the default settings usable with Travis/Ubuntu Python
Travis builds pycaffe
Merge pull request #732 from longjon/travis-pycaffe

Have Travis build pycaffe
Add phase, level, and stage to LayerParameter to define when each layer
will be used.
Incorporate net, net_param, level, stage into Solver/Net.
FilterParam method called from Net::Init excludes layers that the
user specified shouldn't be included in the current phase, level, or
stage.
Use unified train/test nets in examples.