Adjust SVG styling a little.

This works better with the Android stock browser.
Improve the graph clipping a little.
Simplify pie chart creation.

Draw actual segments rather than mess about with circles and clipping.
Add some comments to the graph lib.
Graphing fixes.

Clip some out-of-range values (pie charts).
Use the most recent 100 games for the per-player stats-per-game graphs.
Limit output precision (for mass data) to 5 significant digits.

≥10 is overkill for our needs (consider zooming in and viewport limitations).
Also, less data to be transmitted.
Remove a redundant disc.
Explicitly say when a pie chart shows no results.
Set a sensible default locale (if possible).
Account for some FP inaccuracy when drawing the graph axes.

Yes, we still have additive inaccuracy, but that's low-level noise.
Not enough is accumulated to be a problem other than for comparisons.
Render kills-per-{game,minute} graphs if there's something worth rendering.

When the graph isn't rendered:
• Games less than one minute long
• Games with no kills
• Players who've not yet played two games
• Players who've not killed or been killed