Include print view for substitutions

Close #60 (closed)

aleksis/apps/chronos/settings.py

+from django.utils.translation import gettext_lazy as _
+
+CONSTANCE_CONFIG = {
+    "CHRONOS_SUBSTITUTIONS_PRINT_DAY_NUMBER": (2, _("Number of days shown on substitutions print view")),
+}
+CONSTANCE_CONFIG_FIELDSETS = {
+    "Chronos settings": ("CHRONOS_SUBSTITUTIONS_PRINT_DAY_NUMBER",),
+}