Visualize sizeInsertions and sizeDeletions data

[jhansche]

Sum the insertions and deletions per author to display in an overview.

Nice-to-have: perhaps some kind of chart over time, showing lines changed (added/removed). Consider this similar to the "Contributors" chart in GitHub. Similarly, rather than breaking down to commits per month and comments per month, also consider SLOC-changed per month, especially over time.

Reason for this is that sometimes commit velocity is not sufficient to give a good indication of what kind of work is being done. But SLOC insertions/deletions over time might be a better view (for some people). So having the option to see both views, or combination (like average SLOC per commit) would help give more detail.