Feature Request: add support for tcursor.next()

[gabegattis]

We are using tingodb for our storage tests in BWS. This works pretty well, but there is one problem. Tingodb does not support everything that mongodb does, so there are some things that we would not be able to test.

One example is the cursor.next() method. Tingodb does not support it, so we have to do cursor.toArray() and then grab the first element from the array. This works, but its a bit hacky. It would be helpful if tingodb had support for .next().

[x2es]

Big collections without support of iterators is useless (