DOC: Add missing line separator for ingroup ITKCommon
DOC: Add missing line separator for ingroup ITKCommon

The MetaDataObject class is ingroup ITKCommon. The
ingroup specifier should be a  separate paragraph
so that reflowing the paragraph comments does
not break doxygen indexing.

hjmjohnson/ITK,hjmjohnson/ITK,Kitware/ITK,LucasGandel/ITK,Kitware/ITK,hjmjohnson/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,thewtex/ITK,Kitware/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,richardbeare/ITK,LucasGandel/ITK,malaterre/ITK,vfonov/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,BRAINSia/ITK,vfonov/ITK,hjmjohnson/ITK,hjmjohnson/ITK,BRAINSia/ITK,thewtex/ITK,malaterre/ITK,richardbeare/ITK,thewtex/ITK,vfonov/ITK,malaterre/ITK,malaterre/ITK,Kitware/ITK,vfonov/ITK,malaterre/ITK,hjmjohnson/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,LucasGandel/ITK,BRAINSia/ITK,BRAINSia/ITK,richardbeare/ITK,Kitware/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,thewtex/ITK,vfonov/ITK,richardbeare/ITK,BRAINSia/ITK,Kitware/ITK,malaterre/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,BRAINSia/ITK,richardbeare/ITK,vfonov/ITK,vfonov/ITK,malaterre/ITK,LucasGandel/ITK,richardbeare/ITK,BRAINSia/ITK,richardbeare/ITK,thewtex/ITK,InsightSoftwareConsortium/ITK