A few small performance improvements here and there:
- Don't update level-loading progress bar more than 20 times per sec (slight load time improvement for large maps)
- Don't concat strings in ChatInputScreen -- saves many thousands of temp string allocations per second.
- Stop using non-generic collection for particles. This may be further improved by Deque, since there's a lot of out-of-order element removal going on.
- Remove needless bitwise-AND in Level.getTile
- Replace obsoleted Vector<T> with ArrayList<T> for chat log.