Weight initialization

The tool now has an extra option (initialize_uniform_weights).
If set to w!=0, then the nn weights are set within a uniform
(-w,w). Otherwise, it uses default hardwired weight initialization.

initialize_uniform_weights is set to 0.05, per bbn paper.
if the implementation is in the header, it's implicitely inline I think. Can you move the impl to cpp file (and keep inline if you wish) ?