ENH: simplify code and properly support long long type
ENH: simplify code and properly support long long type

unsigned long long is written as vtktypeuint64
long long is written as vtktypeint64
(these two types were previously cast to ulong and long on write)

long double is kept and written as non-existent vtk type long_double
instead of implicitly casting it to double

Also removing obvious, repetitive and therefore useless comments

Change-Id: If5ec684ef3ad733589868c1e730c3ab4c2c82d02

LucasGandel/ITK,vfonov/ITK,fbudin69500/ITK,blowekamp/ITK,malaterre/ITK,InsightSoftwareConsortium/ITK,spinicist/ITK,fbudin69500/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,malaterre/ITK,Kitware/ITK,InsightSoftwareConsortium/ITK,InsightSoftwareConsortium/ITK,Kitware/ITK,blowekamp/ITK,Kitware/ITK,BRAINSia/ITK,hjmjohnson/ITK,malaterre/ITK,thewtex/ITK,vfonov/ITK,spinicist/ITK,stnava/ITK,Kitware/ITK,spinicist/ITK,BRAINSia/ITK,blowekamp/ITK,spinicist/ITK,stnava/ITK,blowekamp/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,malaterre/ITK,hjmjohnson/ITK,spinicist/ITK,stnava/ITK,LucasGandel/ITK,fbudin69500/ITK,BRAINSia/ITK,richardbeare/ITK,blowekamp/ITK,malaterre/ITK,richardbeare/ITK,vfonov/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,spinicist/ITK,LucasGandel/ITK,stnava/ITK,fbudin69500/ITK,stnava/ITK,thewtex/ITK,fbudin69500/ITK,LucasGandel/ITK,hjmjohnson/ITK,stnava/ITK,BRAINSia/ITK,spinicist/ITK,fbudin69500/ITK,hjmjohnson/ITK,vfonov/ITK,malaterre/ITK,richardbeare/ITK,LucasGandel/ITK,hjmjohnson/ITK,hjmjohnson/ITK,richardbeare/ITK,vfonov/ITK,spinicist/ITK,Kitware/ITK,BRAINSia/ITK,malaterre/ITK,InsightSoftwareConsortium/ITK,thewtex/ITK,stnava/ITK,spinicist/ITK,stnava/ITK,vfonov/ITK,Kitware/ITK,vfonov/ITK,LucasGandel/ITK,blowekamp/ITK,blowekamp/ITK,richardbeare/ITK,richardbeare/ITK,blowekamp/ITK,thewtex/ITK,LucasGandel/ITK,richardbeare/ITK,thewtex/ITK,Kitware/ITK,malaterre/ITK,vfonov/ITK,stnava/ITK,vfonov/ITK,thewtex/ITK,fbudin69500/ITK,malaterre/ITK,fbudin69500/ITK,thewtex/ITK