Revert "Get rid of variants files"

cmake/LofarInit.cmake

cmake/variants/CLANG.cmake

cmake/variants/GNU.cmake

cmake/variants/GNUCXX11.cmake

cmake/variants/GNUCXX11_2018.cmake

cmake/variants/GNUCXX11_CEP4.cmake

cmake/variants/variants

cmake/variants/variants.bob

cmake/variants/variants.buildhostcentos7

cmake/variants/variants.buildhostcentos7test

cmake/variants/variants.cbm200

cmake/variants/variants.cbm201

cmake/variants/variants.cbm202

cmake/variants/variants.cbm203

cmake/variants/variants.cbm204

cmake/variants/variants.cbm205

cmake/variants/variants.cbm206

cmake/variants/variants.cbm207

cmake/variants/variants.cbm208

cmake/variants/variants.cbm209