Cluttered pie charts on school dashboard and maybe elsewhere

[Ghislain Hachey]

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[Brian Lewis]

2/3 of these are now resolved by using onChartRender together with ChartOps (see #877)

Suggestion is to remove the legend from pie-charts created with RowColChart by default. they can be turned back on using ChartOps if required.

[Ghislain Hachey]

task(Charts): add support for allowedTypes and cleanup school dashboard

Resolves #868, #863, #863

→ <<cset b43ecb12ff17>>