refactor(parameter editor): Refactor for test-ability

Improve the test-ability of the parameter editor by refactoring the into:
  - a data_model (business logic)
  - the frontend (UI logic)
Fixed GUI slowdown when many parameter were displayed
  - It used to perform a O(n²) search, now it performs no search at all
  - Keep a pointer to the change reason widget instead of searching for it

Author: amilcarlucas