[Rock-dev] envire: possible breakage in deserialization for users of Grid (and subclasses)

[Sylvain Joyeux]

I have a branch in which I changed how grids are saved. The highlight of 
that change is that one does not have to define a subclass of Grid<T> to 
get proper serialize/unserialize behaviour.

The root of the change is that the layer list is saved in the scene file.

Now, here's the catch: I tried to keep backward compatibility, but I 
have no environments to test the code on ... Could someone try it on 
environments he has ?

NOTE: if nobody yells before the end of the week, I will interpret it as 
either "it works" or "noone has old environments they care enough about"

The code is on the mls_slope branch of slam/envire.

Thanks

Sylvain