Three small bugfixes
- Deduce return types using
decltype(auto)
inBaseOperatorPropertiesMixin<...,2>
- Add missing include in
elementcoloring.hh
- Rename internal method
ProductWithNullaryOperator::operator0()
tobaseOperator()
, because this is what the mix-in base class requires. - Rename internal method
ProductWithNullaryOperator::operator1()
tonullaryOperator()
, because this is more consistent with the class name.