First set of build system patches for Qt5 support.

These changes enable support for Qt5 in CTK libraries and CTK Qt plugins.
Set the CTK_USE_QT5 CMake variable to ON on specify the Qt5 installaltion
directory in QT5_INSTALL_PREFIX.
This commit enables Qt5 support for the CTK Core library, issue #277.

There is still a Qt5Widgets dependency, see issue #278. The tests
pass (on my Ubuntu 12.04 development machine) with both Qt4 and Qt5.
Add support for Qt5

Todo:
* Test with Qt4
* Make sure ctkMacroWrapPythonQt.cmake works correctly
Merge branch 'master' into qt5

Conflicts:
	CMake/ctkMacroGenerateMocs.cmake
	CMake/ctkMacroSetupQt.cmake
	Libs/Core/Testing/Cpp/CMakeLists.txt
	SuperBuild.cmake
Merge remote-tracking branch 'j2/add-qt5-support' into qt5

Conflicts:
	CMake/CTKConfig.cmake.in
	CMake/ctkMacroBuildLib.cmake
	CMake/ctkMacroBuildPlugin.cmake
	CMake/ctkMacroBuildQtPlugin.cmake
	CMake/ctkMacroGenerateMocs.cmake
	CMake/ctkMacroSetupQt.cmake
	CMake/ctkMacroWrapPythonQt.cmake
	CMake/ctkScriptWrapPythonQt_Light.cmake
	CMakeExternals/PythonQt.cmake
	CMakeExternals/VTK.cmake
	Libs/Core/Testing/Cpp/CMakeLists.txt
	Libs/Core/Testing/Cpp/ctkAbstractLibraryFactoryTest1.cpp
	Libs/Core/ctkAbstractLibraryFactory.h
	Libs/Core/ctkAbstractLibraryFactory.tpp
	Libs/Core/ctkCheckableModelHelper.cpp
	Libs/Core/ctkErrorLogQtMessageHandler.cpp
	Libs/Core/ctkErrorLogQtMessageHandler.h
	Libs/Testing/ctkTest.h
	Libs/Widgets/Testing/Cpp/CMakeLists.txt
	Libs/Widgets/ctkCoordinatesWidget.h
	Libs/Widgets/ctkMaterialPropertyPreviewLabel.cpp
	Libs/Widgets/ctkPopupWidget.cpp
	SuperBuild.cmake
Use Qt5 CMake 2.8.12 features.

Also move Widget dependent classes from Core to Widgets. Closes #278.
Qt5 compatibility for almost all libraries.

Not working yet:

 - XNAT libraries
 - VTK dependent libraries
 - Python Wrapping
Do not assume a specific Qt5 install structure.
Make more libs and apps compatible with Qt5.
Use Qt5 compatible qRestAPI version.
Fix Qt5 dependencies in case only CTK_BUILD_ALL is enabled.
Merge branch 'qt5'

* qt5:
  Fix Qt5 dependencies in case only CTK_BUILD_ALL is enabled.
  Use Qt5 compatible qRestAPI version.
  Make more libs and apps compatible with Qt5.
  Do not assume a specific Qt5 install structure.
  Qt5 compatibility for almost all libraries.
  Use Qt5 CMake 2.8.12 features.
  Add support for Qt5
  This commit enables Qt5 support for the CTK Core library, issue #277.
  First set of build system patches for Qt5 support.