BUG: fix backward compatibility of sample data logic methods

Since the new generic API returns lists of loaded nodes, the
backward compatibility methods need to return the first element
rather than the list.

py_ThresholdThreadingTest
py_StandaloneEditorWidgetTest
py_sceneImport2428
py_ViewControllersSliceInterpolationBug1926

http://slicer.cdash.org/testDetails.php?test=4166721&build=129681
http://slicer.cdash.org/testDetails.php?test=4166722&build=129681
http://slicer.cdash.org/testDetails.php?test=4166791&build=129681
http://slicer.cdash.org/testDetails.php?test=4166797&build=129681

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22225 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix build error occurring when OpenSSL support is disabled

While commit r22220 added SSL support ensuring the CMake option
"Slicer_USE_PYTHONQT_WITH_OPENSSL" was disabled by default. Not all OpenSSL
related code was properly excluded, this commit ensures Slicer can be
compiled with OpenSSL support disabled.

Discussion: http://slicer-devel.65872.n3.nabble.com/Windows-build-fails-due-to-missing-QSslSocket-class-tt4029446.html

See issue #2998 and #2355

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22226 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Fix unused variable warning in qMRMLSliderWidget

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22227 3bd1e089-480b-0410-8dfb-8563597acbee