Change scale.beginAtZero default to true

[benmccann]

This would make it easier to tell how large values are relative to each other. It's frequently called out as misleading to not have bar chart axis start at 0. Some examples:
https://callingbullshit.org/tools/tools_misleading_axes.html
https://flowingdata.com/2015/08/31/bar-chart-baselines-start-at-zero/

Also, now the scale can begin at the lowest value making that value not appear on the chart, which is confusing. Changing the default of this value would fix that issue as well:
#5938 (comment)

[sebiniemann]

Would be great, we set this for all our graphs 😅