Add stage2 results for california_housing. Add weight density plots for stage 2 exps

results/kin8nm/stage2/weight_density_normalize_weights.png

results/kr-vs-kp/stage2/weight_density_no_normalization.png

results/kr-vs-kp/stage2/weight_density_normalize_D.png

...r-vs-kp/stage2/weight_density_normalize_D_and_weights.png

results/kr-vs-kp/stage2/weight_density_normalize_weights.png

results/spambase/stage2/weight_density_no_normalization.png

results/spambase/stage2/weight_density_normalize_D.png

...pambase/stage2/weight_density_normalize_D_and_weights.png

results/spambase/stage2/weight_density_normalize_weights.png