BUG: qMRMLLayoutManagerTest(s) - Fix (Selection|Interaction)Node warnings

This commit will fix the following warnings:

147: Warning: In /home/jchris/Projects/Slicer/Libs/MRML/DisplayableManager/vtkMRMLAbstractDisplayableManager.cxx, line 583
147: vtkMRMLThreeDReformatDisplayableManager (0x2c92750): CreateIfPossible - MRMLScene does NOT contain any InteractionNode
147:
147: Warning: In /home/jchris/Projects/Slicer/Libs/MRML/DisplayableManager/vtkMRMLAbstractDisplayableManager.cxx, line 591
147: vtkMRMLThreeDReformatDisplayableManager (0x2c92750): CreateIfPossible - MRMLScene does NOT contain any SelectionNode

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22533 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Fix qMRMLLayoutManagerTest2

Ensure ModelDisplayableManager properly delete resources when
a new scene is set.

Ensure the slicer logic set the scene on layers when a new
scene is set a second time.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22534 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: Re-organize qMRMLLayoutManagerTest(1|2|3|4) for easier readability

Factor out code into convenience functions:
 - checkViewArrangement
 - checkNumberOfItems

Use vtkNew when possible

There is no need to explicitly delete the layout manager since
it was a QWidget instantiated on the stack as a parent.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22535 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: Update "removeSliceView" to be consistent with other remote methods

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22536 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Update qMRMLLayoutManagerTest2 to check for reference count

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22537 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Improve readability of MRML tests using vtkNew where possible

Simplify code removing tests for null object already being done
in the helper macro "EXERCISE_BASIC_OBJECT_METHODS"

For example, the following should not be needed:

  vtkNew<vtkFoo> foo;
  if (foo.GetPointer() == 0)
  {
    std::cerr << "Failed to instantiate vtkFoo" << std::endl;
  }

Instead, the following should be used:

  EXERCISE_BASIC_OBJECT_METHODS(foo.GetPointer())

Remove use of unnecessary vtkSmartPointer to check return value. Indeed,
since the operator "==" of the vtkSmartPointer is overloaded to compare with
the pointed object, there is no need to used a smart pointer. [1]

// ---------
vtkSmartPointer<vtkMRMLDisplayableNode> pnode = node1->GetDisplayableNode();
std::cout << "GetDisplayableNode returned "
          << (pnode == NULL ? "null" : "not null")
          << std::endl;
// ---------

has been changed into

// ---------
vtkMRMLDisplayableNode* pnode = node1->GetDisplayableNode();
std::cout << "GetDisplayableNode returned "
          << (pnode == NULL ? "null" : "not null")
          << std::endl;
// ---------

[1] https://github.com/Kitware/VTK/blob/0e0674a3695fdeaf01ce87dfc04e32111b7402e0/Common/vtkSmartPointerBase.h#L104

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22538 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Improve readability using vtkNew where possible

In addition to be shorter, it simply conveys the idea of locally
instantiating an object.

Indeed, vtkNew allow to instantiate an object on the heap and deleting it
when it goes out of scope if its reference count has been incremented by
either assigning the object to a smart pointer or calling Register.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22539 3bd1e089-480b-0410-8dfb-8563597acbee