Improving callback functions #57

I'd like to open a discussion on how we can improve callback functions:

1. The way simulation data is set is non-standard, or different from other optimization libraries (scipy etc.). A suggestion is to take parameters as an input and output simulation data.
2. In connection to 1, if more functionality is required. Should additional callback functions (error handling, etc, post or pre callback) may be introduced?
3. Located in the DynamicSystems class, it is not possible to access additional information from other classes (like inference)
4. If the user require special functionality, documention how it can be done and possible common cases should be made. For example writting a new BayesianCalibration.run() function.