The current rolling fast filter has a high false negative rate and causes the repeated resending of inv's to nodes that we just received inv's from; By using a generational approach we can avoid this issue caused by erasing data from the filter and so we can use this rolling filter in place of a regular bloom filter and improve overall performance under load significantly.

Still needs a bit of work adding benchmark tests and cleaning up. Probably I should leave the old rolling filter in place so we can see the performance difference in the benchmark tests.

have getdata block invs return something (notfound or reject) on error. Silently dropping a reply makes clients time out and assume that the node is dead or slow