DynamicList improvements/disambiguities

* DynamicList::allocSize(label)
  - Adjust the allocated size. The addressed list can be truncated but not
    extended, use setSize() for that.

* DynamicList::reserve(label)
  - Reserve allocation for *at least* this number of elements.
    Never shrinks the allocated size, nor touches the addressed list size.

* DynamicList::setSize(label)
  - proposed behaviour:
    Adjust the addressed list size, allocating extra space if required.
  - The current behaviour is ambiguous about what addressable size will
    actually get set and using it to extend the addressable size (as
    per List) automatically shrinks the allocated space to this size!