No initial inplace

added error checking of consider_constant

changed min_informative_str to use spaces instead of tabs

this improves legibility of large graphs

Rebased new lazy ifelse

I want to order them according to the order in the sequential shell
that calls them.

As for grad and Rop, I am now taking care that if the input is a list I
return a list (regardless of the number of elements).

There was a confusion in the naming of the two branches of the ifelse.

Specifically I insisted on the fact that the ifelse can deal with multiple
tensors on the then/else branches.

As James provided in the coments, cond might be misleading, since is usually
associated to something si,ilar to a switch clause.