Review 'allowedTypes' in dashboard charts

[Brian Lewis]

By default, the binding allowedTypes is not present in the RowColChart, so you do not see the type selection toolbar.

Teachers Dashboard has been modified with examples of using specific allowed types, or , alternatively, specify keyword ‘all’

This adds quite a bit of functionality to dashboards; in particular because we can now get a selection of types “for free” from one component.

This for example may mean that the number of components on e.g. SchoolDashboard can be reduced?

@Ghislain Hachey would appreciate you going through these , and assigning allowedTypes depending on what makes sense ( e.g. ‘line’ and ‘area’ don't make sense with categorical data)

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[Ghislain Hachey]

I’ve added it to a few places which as a result I could eliminate some of the no longer used plottable directive completely. I also did a bit of polish to the school dashboard. I will bring this polish to other contexts and at the same time look at #878

[Ghislain Hachey]

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

Resolves #868, #863, #863

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