Add deaths_log to track deaths not caused by a hero

[jiapengfei]

Current Behavior
Team scores may be not equals to total kills number or total deaths number. This is due to the neutrals kills are not team scores, but tower kills are team score. And both of them are not player kills.

Expected behavior/code
Now the kill_by only have the numbers. Like the kills log, can we create death logs with times? Or how can I get the similar result from current APIs?

[howardchung]

I believe this idea has been discussed, but not yet implemented.