recode functions involving predictions

[courtiol]

The upcoming version of spaMM (2.2) no longer require the predictions to be chunked.
As the spaMM functions are faster than our work around, we should remove the work around.
That will also lead to shorter code.

[courtiol]

spaMM changes are not entirely solving the issues stemming from very large predictions so this will have to wait for further spaMM releases.

[courtiol]

try again, François solved the issue

[courtiol]

Duplicate #150