DOC: Update .mailmap to consolidate author identification
DOC: Update .mailmap to consolidate author identification

Use consistent names in release notes, etc. by setting .mailmap entries.
See *MAPPING AUTHORS* in `git help shortlog`.

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