Make parameter "indices" deprecated

[merretbuurman]

I introduced indices to allow passing several handle record indices.

But now we allow passing various options which are appended to the HTTP GET request (e.g. type, which results in ?type=bla being appended to the Handle Server URL). So why should we not let users directly use index for indices?

In case of type, we allow passing lists. So, type=['bla', 'bli'] will result in ?type=bla&type=bli. We could do the same with index.

Opinions?