This changes the internal type that is used to signal that a vector
is unspecified from any to void.
I tried to verify that the behavior of Bro is still the same. After
a lot of playing around, I think everything still should worl as before.
However, it might be good for someone to take a look at this.
addresses BIT-1144
observed elements.
Add methods to merge with and without pruning (before only merge
method was with pruning, which invalidates the number of total
observed elements)
I am not (entirely) sure that this is mathematically correct, but
I am (more and more) getting the feeling that it... might be.
In any case - this was the last step and now it should work
in cluster settings.
Note: merging top-k data structures is not yet possible (and is
actually quite awkward/expensive). I will have to think about
how to do that for a bit...
