Add support for task reordering based on ordering history

Hi lads, this MR changes the behaviour for the task switcher:

• tasks are ordered following SortLastActivated sort mode: the rightmost task will be the last activated one, remaining tasks are sorted following their own opening history as well
• a new difference between swiping tasks or open them from task switcher has been introduced: switchingFromActiveTask

Depends: Plasma Mobile: Add a new sort mode and relative handler in TasksModel)
Should close: [taskswitcher] Sort by opening history