[TASK] Add balance_change array to transaction response, computed from metadata

Google's needs are different from ours. The Google style guide evolved to serve the least common denominator of tens of thousands of developers with a broad range of competency. Ripple Labs on the other hand needs to serve a smaller number of developers whose competency is enormously beyond average. "A foolish consistency is the hobgoblin of little minds..." (Emerson) Consistency for consistency's sake provides no value. A hard style rule should only be adopted if it provides a concrete, measurable value and not because it satisfies the writer's faith. I'm with Brandon on this one.