Django-admin-charts

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* add permissions
* add missing migration
* check missing migrations during testing
* remove duplicate black check

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* migrate to django-memoize from unmaintained django-cache-utils
* testing passes in Django 4.1

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* pefrormance fixes
* show info when no dashboard stats are available

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* store chart values in CachedValue table in DB to make charts with more complicated queries faster
* add refresh/refresh all/reload on change controls to the charts
* use unpkg versions of nvd3/d3 libraries as default to simplify initial configuration

* set ``ADMIN_CHARTS_NVD3_JS_PATH``, ``ADMIN_CHARTS_NVD3_CSS_PATH``, ``ADMIN_CHARTS_D3_JS_PATH`` variables if you want to continue using your internal JS files

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* fix problem where in queries with count limit the choices could have been shuffled

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* fix broken admin index page