Add array->last_where, reshuffle first*/last* methods

Should add some sanity:

  first_where / last_where
  first_index / last_index

->first, ->firstidx still exist for backwards compat

	modified:   lib/List/Objects/WithUtils/Role/Array.pm
	renamed:    t/01_array/firstidx.t -> t/01_array/first_index.t
	new file:   t/01_array/first_where.t
	renamed:    t/01_array/lastidx.t -> t/01_array/last_index.t
	renamed:    t/01_array/first.t -> t/01_array/last_where.t