Add DiamondDualConnectivityManager and DiamondDualMeshManager

These mechanisms are designed to manage diamond meshes/connectivities

The main idea is that the diamond mesh is stored as long as its
primary mesh lives, and can be retrieved easily.

The same mechanism is defined for diamond mesh connectivities. Thus in
a moving grid context, the only required calculations will be the
definition of the diamond mesh's vertices coordinates.

Recall that diamond meshes are just meshes so all meshes'
functionality apply to them.