Enable distributed copying of the indices on one machine

I'm working on exporting a very large data set (1,1TB) from ES 0.20.5, so it's a pain in the ass to do it with what this offers right now (would take me 36 days according to my 1-hour test).

So what I have implemented is processing of multiple indexes at a time, support of basic auth and a few handy features. Anyway, pull request is not entirely complete (it wont work with some combinations of the arguments passed to the process), but overall should be good enough for what its needed.