Add save/load for the CNN

[ArtLinkov]

Admittedly, it took a while until we got some time on our hands to work on this... :) We should have it done by the end of the week. For now, save/load to JSON will be supported.

[fab1an2]

Save yes but similar Marshal (from Ruby) I woul like to export to C.

For example I learn in crystal, test in crystal and when finish create a C file with only one function. All weights, bias etc. are inside C. Only put input data and get output int shainet(data *input, output...) {

[bararchy]

@fab1an2 saying that here: https://github.com/NeuraLegion/crystal-fann/issues/11 was enough :) It's a crystal thing, not related to either crystal-fann or SHAInet