* fix(command): Added command and hotkey binding for navigate to next and previous display set.
* Centralized the sorting (function) of display sets since at least three
areas sort display sets: hanging protocols, study/thumbnail browser and
updateViewportDisplaySet command.
* Renamed some methods for clarity.
* Scrolling active thumbnail into view for an updateViewportDisplaySet
* Added a null check.
* Added check to minimize thumbnail scrolling.