Remove ITK legacy code in Superbuild
Remove ITK legacy code in Superbuild

By default set ITK_LEGACY_REMOVE to ON, to aid in consistent behavior
with ITK.

SimpleITK/SimpleITK,SimpleITK/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,InsightSoftwareConsortium/SimpleITK,SimpleITK/SimpleITK,richardbeare/SimpleITK,SimpleITK/SimpleITK,richardbeare/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,SimpleITK/SimpleITK,SimpleITK/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,richardbeare/SimpleITK,blowekamp/SimpleITK,richardbeare/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,richardbeare/SimpleITK,SimpleITK/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,richardbeare/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK,InsightSoftwareConsortium/SimpleITK,blowekamp/SimpleITK