Use new icon set in boolean table columns

Subclass of django-tables2 boolean column, change render(...), to use with iconify icons. Needed for e.g. DashboardWidgets or other apps (e.g. Alsijil)

added part::frontend label

changed title from Use new icon sett in boolean table columns to Use new icon set in boolean table columns

mentioned in issue AlekSIS-App-Alsijil#200 (closed)

Obsoleted by #696 (closed)

closed