Change memory allocator on scalar variables (item-kind none)

[DavidDureau]

With an environment variable, we would like to choose if scalar (resp. array) variables (item-kind="none") are allocated with cudaMallocManaged or with the standard memory allocator.

[grospelliergilles]

I have look at your issue. I think it will not work if this is done for all variables with item-kind=="none" because for materials, partials values are these kind of variables and so they will not be accessible on accelerators. Do you need this only for some variables ?