Update 7.1 stats added

Stats for update 7.1 have been added. Now tank pages are available to all tiers for current and previous main udpate version.

Premium tanks (and especially the pricey loot-box tanks) continue to dominate the tier VIII stats tank rankings. 13 out of 15 best performing tanks are premium tanks. Is the game slipping step-by-step towards Pay-2-Win?

plot of chunk fig_tanks_tier8_rWR