destructive non-bang methods

[dunric]

There is a misconception with the following instance methods:

fill vs fill! and indgen vs indgen!

In current implementation the former ones are just aliases to the latter, which is quite confusing and against not only basic ruby naming conventions but also in contradiction to other NArray methods naming like collect/collect!, newdim/newdim!, newrank/newrank! or flatten/flatten!.

I'd suggest fill and indgen have to either call their non-destructive function versions or be rather completely removed.