Allow get the number of result by action

[Elbandi]

This patch allow get the buld response status by action. Same result as len(r.Updated()), etc. but more performance (mostly in big bulk request)

[olivere]

What's wrong with len(Indexed()) etc.?

[olivere]

As for performance: Can you provide a benchmark?

[Elbandi]

i havent benchmark :( but just looked into the source: ByAction build a new items array.

if the bulk has >100k items, thats not only lots of cpu (fields memory copy) usage, but also high memory usage ~12Mb (pure sizeof(BulkResponseItem) == 128) too.