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* make possible to change dateformat of x axis <Petr Dlouhý>
* add example for dynamic criteria <Petr Dlouhý>
* test also dynamic criteria <Petr Dlouhý>
* use django-qsstats-magic that work with Python 3 in tests <Petr Dlouhý>
* test actual chart generation -> increase test coverage <Petr Dlouhý>
* fix: preserve criteria settings of other chart stats <Petr Dlouhý>
* fix duplicate id of dynamic criteria form <Petr Dlouhý>
* reduce size of generated code by reusing load_charts code in function <Petr Dlouhý>
* fix duplication of % sign in template svg tag <Petr Dlouhý>
* catch also TypeError in registration field <Petr Dlouhý>
* rename "Graph key" to "Graph identifier" to be more clear <Petr Dlouhý>
* use save_as=True in admin to allow easier copying of charts <Petr Dlouhý>
* allow to override day intervalse for graphs <Petr Dlouhý>
* reorganize testing to run coverage <Petr Dlouhý>
* remove old import code <Petr Dlouhý>
* checks of DashboardStats field values, report field errors by Django message framework <Petr Dlouhý>