Arjen bugfix event size

### Problem
1. event aggregate did not count events on brush move
2. event radius did not update properly on brush move

### Solution
1. pass proper time start and end to counter function when animation is enabled.
2. update radius when events are drawn again on brush move.

### Note
Solution 2. is a hack including duplicate code; a proper solution should be implemented.

This solves https://github.com/nens/lizard-nxt/issues/261