Add view tests

• Introduce framework to simply test correct rendering of views
• Create tests for dashboard views
• Create tests for plan views
• Create tests for default admin views (add and change) of AKModel models
• Create tests for scheduling (admin) views
• Create tests for submission views
• Improve pipeline to correctly run the new tests on a blank database with fixture loading
• Add coverage reporting
• Show test results in GitLab directly

AKDashboard/fixtures/dashboard.json

+[
+{
+    "model": "AKDashboard.dashboardbutton",
+    "pk": 1,
+    "fields": {
+        "text": "Wiki",
+        "url": "http://wiki.kif.rocks",
+        "icon": "fab,wikipedia-w",
+        "color": 2,
+        "event": 2
+    }
+}
+]