rename and refactor the Laplace method

@karlnapf 
take a look at this.
This just the first step of refactoring the Laplace method.
In near future, I will slightly refactor the Laplace method again using strategy pattern.
For now (GSoC period),  user have to use a specific Laplace class.
maybe (in another pr) add the comment that all laplacian inference methods would inherit from this class