* origin/topic/bernhard/topk:
adapt to new folder structure
fix opaqueval-related memleak
synchronize pruned attribute
potentially found wrong Ref.
add sum function that can be used to get the number of total observed elements.
in cluster settings, the resultvals can apparently been uninitialized in some special cases
fix memory leaks
fix warnings
add topk cluster test
make size of topk-list configureable when using sumstats
implement merging for top-k.
add serialization for topk
make the get function const
topk for sumstats
well, a test that works..
implement topk.
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.
