Application of patch suggested in...

Application of patch suggested in https://bugs.kde.org/show_bug.cgi?id=446020#c1 plus minor cleanups

umbrello/umlscene.cpp
- In function addWidgetCmd print debug message showing widget's x and y
  coordinates.
- In function setupNewWidget,
  - remove unneeded parentheses in if-condition testing w->isPinWidget()
    and others;
  - call UMLApp::app()->setCurrentView with activeView() as argument.
- In function dropEvent loop over tidList, on calling setupNewWidget
  provide `true' for argument setPosition.
- At functions selectedCount, setClassWidgetOptions fix minor issues in
  documentation.
- In function resizeSceneToItems, as an experimental change comment out
  call to setSceneRect(itemsBoundingRect()).
  It appears that the function resizeSceneToItems may be removed
  altogether (subject to further tests).

CCBUG: 446020