Restructure examples in documentation

[bartvanerp]

Following up on #94 and also our own observations about the documentation section, we need to restructure it. The idea is to split the example section into two (or more) subsections: basic examples and advanced examples, where the latter one includes the custom and more complicated nodes that we have designed over the years.

[bartvanerp]

Initial proposal:

1. Coin toss model (Beta-Bernoulli)
2. Bayesian Linear Regression
3. Active Inference Mountain car
4. Chance-Constrained Active Inference
5. Assessing People's Skills
6. Gaussian Linear Dynamical System
7. Ensemble Learning of a Hidden Markov Model
8. Autoregressive Model
9. Hierarchical Gaussian Filter
10. Bayesian ARMA model
11. Infinite Data Stream
12. System Identification Problem
13. Univariate Gaussian Mixture Model
14. Multivariate Gaussian Mixture Model
15. Gamma Mixture Model
16. Universal Mixtures
17. Global Parameter Optimisation
18. Invertible neural networks: a tutorial
19. Conjugate-Computational Variational Message Passing (CVI)
20. Solve GP regression by SDE
21. Nonlinear Smoothing: Noisy Pendulum
22. Nonlinear Smoothing: Rabbit Population
23. Nonlinear Virus Spread
24. Nonlinear Sensor Fusion
25. Kalman filter with LSTM network driven dynamic
26. Handling Missing Data
27. Custom Nonlinear Node
28. Probit Model (EP)
29. RTS vs BIFM Smoothing
30. Advanced Tutorial

Change to

Basic examples

1. Modeling a coin toss (1)
2. Bayesian linear regression (2)
3. Hidden Markov modeling (7)
4. Kalman filtering and smoothing (6, 11, 17, 26)
5. Non-linear Kalman smoothing (21, 22, 23, 24, 25)

Advanced examples

1. Advanced RxInfer tutorial (30)
2. Nonlinear modeling with CVI (12, 19)
3. Solve GP regression by SDE (20)
4. Mountain car (3)
5. Chance-Constrained Active Inference (4)
6. Assessing People's Skills (5)

Custom nodes

1. Specifying a custom node (27)
2. AR Node: … (8, 10)
3. GCV Node: … (9)
4. Mixture Node: … (16)
5. Normal Mixture node: … (13, 14)
6. Gamma Mixture node: … (15)
7. Flow node: … (18)
8. Probit node: … (28)
9. BIFM node: … (29)

[albertpod]

ping @bartvanerp, I think we can proceed with the update. WDYT?

[bartvanerp]

Yes we should. Let's invest some time next week