Updated GDCM to version 2.2.1 and ITK to version 4.2.1 in superbuild.

Wrote patch for ITK 4.2.1 to work with external GDCM 2.2.1.
Fixed clone methods in core.

Since ITK introduced clone methods in their base classes MITK clone methods
collide with them. I adapted the mitkCloneMacro to be compatible with ITK.
All "Clone()" methods were renamed to "InternalClone()" and return a
pointer to a LightObject instead of an AffineGeometryFrame3D.
InternalClone() is called by ITK's Clone().
Replaced itk::OStringStream by std::ostringstream in core.
Replaced inclusions of itkExceptionObject.h by itkMacro.h in core.
Removed wrong "return NULL" in Geometry3D::GetCornerPoint().
ExpAdded types to calls to templated methods where the compiler can't deduce them anymore (core).
Replaced [Get/Set]_vnl_vector() by [Get/Set]VnlVector() in core.
Added missing virtual keyword to pure abstract methods of BaseData (core).
Fixed another clone method related bug I missed in commit 81afebdb5184959e392a177ce60e1cfcbb947bf9 (core).
Adapted MITKScalarImageToHistogramGenerator to new/renamed ITK classes (MUST BE TESTED!).
Extended ITK4 Migration to QmitkExt
Fixed various smaller ITKv4 migration bugs.
Updated GDCM to version 2.2.1 and ITK to version 4.2.1 in superbuild.

Wrote patch for ITK 4.2.1 to work with external GDCM 2.2.1.
Fixed clone methods in core.

Since ITK introduced clone methods in their base classes MITK clone methods
collide with them. I adapted the mitkCloneMacro to be compatible with ITK.
All "Clone()" methods were renamed to "InternalClone()" and return a
pointer to a LightObject instead of an AffineGeometryFrame3D.
InternalClone() is called by ITK's Clone().
Replaced itk::OStringStream by std::ostringstream in core.
Replaced inclusions of itkExceptionObject.h by itkMacro.h in core.
Removed wrong "return NULL" in Geometry3D::GetCornerPoint().
ExpAdded types to calls to templated methods where the compiler can't deduce them anymore (core).
Replaced [Get/Set]_vnl_vector() by [Get/Set]VnlVector() in core.
Added missing virtual keyword to pure abstract methods of BaseData (core).