Only select enabled activities on the dashboard

[smeeckaert]

Description

There is a problem sometimes with Models that are not configured or enabled in the twill.dashboard.modules config.

The activity is logged for every model regardless of whether or not this Model is displayed in the dashboard. And this is a good thing.

The problem is when the last 20 activities are from an not configured model. When that happens nothing is displayed in the activity section.

This PR changes how the activities are selected by only selecting those which are enabled.