- add copy construct from UList
- remove copy construct from dissimilar types.
This templated constructor was too generous in what it accepted.
For the special cases where a copy constructor is required with
a change in the data type, now use the createList factory method,
which accepts a unary operator. Eg,
auto scalars = scalarList::createList
(
labels,
[](const label& val){ return 1.5*val; }
);