Make sure every solver parameter has a default value

[neo-alex]

🚀 Feature

Add default value to every solver parameter (in their constructor), if possible.

Pitch

It would be convenient for the end-users to easily run all compatible solvers on a given domain, without having to customise right away solver-specific parameters (which today is not always possible, since some solvers lack default values in their constructor), even if the best solution can only be obtained by fine-tuning these parameters of course.