Rework problem class implementations

[tlunet]

Following a template applied to the advectionNd problem class, rework all other implementations to get to the same standards :

• [x] use of the default parameter approach and inheritance from RegisterParams base class (see #206)
• [x] update (with eventual rewrite) of full documentation (see #286)
• [ ] compliance to new problem base interface (see #254)
• [ ] compliance to new Contribution Guidelines