[Toaster] RFC - showing 0 values in tables

[Barros Pena, Belen]

It has been brought to my attention that, since a value 0 is not the same
as value none, we should maybe show 0 values in the task performance
information. 

Although I understand that none is not 0, I still think that, in the case
of task performance information, if the value is 0 I don't need to care
about it, since the task is not consuming any resources. If I don't need
to care about it, why are you showing it to me? I am of the minimalistic
kind.

Having said that, I am happy with both options. I have made the necessary
changes and pushed them to

bbarrosp/show-zeros

so that you can see how it looks like. If you feel strongly one way or
another, please speak out.

Thanks!

Belén