imporve from_genes implementation

[mauicv]

Currently datastore saves the genome structure as all nodes and edges includeing input and output nodes but from_genes hydrator factory expects num_inputs and num_outputs and that the nodes and edge lists passed are only hidden nodes. Hence to use from_nodes with datastore we have to do:

generation = ds.load(generation_in)
nodes, edges = last_gen['best_genome']
input_num = len([n for n in nodes if n[4] == 'input'])
output_num = len([n for n in nodes if n[4] == 'output'])
nodes = [n for n in nodes if n[4] == 'hidden']
genome = from_genes(
    nodes, edges,
    input_size=input_num,
    output_size=output_num,
    weight_low=-2,
    weight_high=2,
    depth=len(LAYER_DIMS))

Similarly computing the number of layers is not trivial and should be just be a value stored in some meta data either on the generation or the DataStore class itself.