This introduces `emplace` and `emplace_or_assign` members
allowing population of the container without copying values in.
It also reworks the batch insertion. On top of adding the ability
to move the elements in (without making a copy) and constructing
them in place, it also makes the non-assign version of the inserter
a lot safer by explicitly asserting the fact that while it was
in use no duplicates were added to the vector. Before now,
the duplicates were just silently removed from the container.
It also optimizes the batch insertion somewhat by using non-stable
`std::sort` for unique case as well as replacing `std::unique`
invocation with `std::find_adjacent`.
This commit fixes a couple of bugs preventing SortedVector and
MutableSet from being serialized.
Also, it introduces minimal testing for serialization.
These data structures are substitutes for a `std::map<Key, Value>` where
`Key` is embedded in `Value`. Their main goal is to be serializable in a
YAML sequence while preserving the order enforced by the key.
`MutableSet` is implemented using a map.
`SortedVector` is implemented using a sorted vector.
Ivan Krysak