Changed _activeCellsForEntities to use vector instead of map.
Added test against initial mesh entities having appropriate active cell counts.
Changed vector size approximation to use capacity instead of size.  Changed MeshTopology::_sidesForEntities to use vector instead of map.
Fixed memory approximation for _sidesForEntities.
Changed _sidesForEntities to use vector instead of set in innermost container.
Changed MeshTopology::_entities to use sorted vector instead of set for the innermost container.
Fixed a test that was making incorrect assertions when run on more than one rank.
Changed MeshTopology::_knownEntities to use sorted vector instead of set as the map key.
Changed _canonicalEntityOrdering to use vector instead of map.