improve handling of competition reward splits that don't sum to 100

Currently we require that a reward split in a competition proposal must add to exactly 100. Perfect precision. It is hard then to have a close split between three winners, has to be 33-33-34. We would like to allow 33-33-33 with leftovers that will flow back to the dao, and even better, higher precision on the proportions to minimize the amount leftover, allowing us to get closer to a sum of 100.