remove massive loops in overall.php (addresses #5)
remove massive loops in overall.php (addresses #5)

- use preinitialized associative arrays instead of separated arrays for
  labels and data
- use GROUP BY instead of separate statements for each possible key in
  all SELECT statements
- simplify JavaScript by using functions from includes/charting.php

coffeestats/coffeestats,coffeestats/coffeestats,coffeestats/coffeestats