Regularized gmms

[emorice]

• [x] Refactor cv
• [x] CV on number of components for gmm
• [x] Same for igmm
• [x] 2-d cv on reg for gmm
• [x] Opt of reg on igmm

[emorice]

Done but the optimized regularized IGMM does not work as intended.

[emorice]

Follow-up in gemz #15