Changes for avoiding access to UMLApp `this` pointer before end of its construction:

umbrello/uml.{h,cpp}
- Factor heavy weight initializations from constructor to new public
  function setup() to be called immediately after construction.
- Change initStatusBar() local variable defaultZoomWdg into UMLApp
  member m_defaultZoomWdg.

umbrello/main.cpp
- In main program case !app.isSessionRestored() call uml->setup() after
  allocating new UMLApp() to uml.