Const-correct Dimension::operator+, - and *.
Const-correct Dimension::operator+, - and *.

sintefmath/equelle,atgeirr/equelle,atgeirr/equelle,sintefmath/equelle,babrodtk/equelle,atgeirr/equelle,sintefmath/equelle,sintefmath/equelle,atgeirr/equelle,atgeirr/equelle,atgeirr/equelle,babrodtk/equelle,babrodtk/equelle,babrodtk/equelle,sintefmath/equelle,sintefmath/equelle,sintefmath/equelle,babrodtk/equelle,babrodtk/equelle,atgeirr/equelle,sintefmath/equelle,babrodtk/equelle,atgeirr/equelle