BUG: Fix "Deleting Unknown Object" warning in all mrml node tests

This commits (1) changes the helper node class name associated with the
hierarchy node to be unique and (2) updates the helper node definitions
to be consistent with the helper node declared in vtkMRMLNodeTest1.

Also remove debug output for vtkMRMLColorNodeTest1 and vtkMRMLUnitNodeTest1.
The extra verbosity was adding "noise" to the test output.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23444 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: Re-organize and simplify vtkMRMLColorTableNodeTest1

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23445 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Change vtkMRMLColorNode::GetColor to explicitly accept array of size 4

The function signature is now consistent with vtkLookupTable::GetTableValue.

Let's also note that when wrapped in python, an error will now be returned
if a list not having exactly a size of four is passed.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23446 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Fix memory initialization in vtkMRMLColorTableNode::SetNumberOfColors

This commit fixes a problem discovered while running the test
vtkMRMLColorTableNodeTest1 through valgrind. It basically ensures that
new table entry are initialized.

==26783== Conditional jump or move depends on uninitialised value(s)
==26783==    at 0x23B631D3: __printf_fp (printf_fp.c:404)
==26783==    by 0x23B62A9B: vfprintf (vfprintf.c:1654)
==26783==    by 0x23B875A4: vsnprintf (vsnprintf.c:119)
==26783==    by 0x2367E01F: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.18)
==26783==    by 0x23684455: std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_float<double>(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, char, double) const (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.18)
==26783==    by 0x2368473F: std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, double) const (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.18)
==26783==    by 0x2368FA34: std::ostream& std::ostream::_M_insert<double>(double) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.18)
==26783==    by 0x511352D: vtkMRMLColorNode::SetNameFromColor(int) (vtkMRMLColorNode.cxx:312)
==26783==    by 0x511336F: vtkMRMLColorNode::SetNamesFromColors() (vtkMRMLColorNode.cxx:295)
==26783==    by 0x512245B: vtkMRMLColorTableNode::SetColor(int, char const*, double, double, double, double) (vtkMRMLColorTableNode.cxx:1301)
==26783==    by 0x48750A: vtkMRMLColorTableNodeTest1(int, char**) (vtkMRMLColorTableNodeTest1.cxx:83)
==26783==    by 0x47215C: main (MRMLCoreCxxTests.cxx:616)

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23447 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Update vtkMRMLColorTableNodeTest1 to test against expected output

This commit updates the test to check that color table entry
can be written and read from a color table file.

Some background into ...

Commit r20729 attempted to implement a test checking that the color table
entry could be written to a scene and read from the scene. The issue was
that the test was only displaying value and was not testing against
expected value.
Then, in commit r22344, the color mrml nodes have been updated to
to not write anymore into the mrml scene.

The test wasn't reporting that no color could be read but was still
passing, this commit updates the test and check for expected values instead
of just displaying them.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23448 3bd1e089-480b-0410-8dfb-8563597acbee