Add a light-weight associative container, API-wise very similar to QMap,
that's based on two sorted continuous containers (QVector by default).
The class is internal for now.
Change-Id: Ife12576c4abb39a3ea2acb0a1ba0faca91b3a4c5
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
