cron jobs should be killed if hang

Each cron job has a "wall time" of 15 minutes. The reason behind is that sometimes it might happen that the cron job hang (in a real time scenario it was RedCap connector that hung, because of some strange network issues). In such situation the job has open DB session that prevents some operations on DB (like applying migration scripts in our real case scenario).

Closes #200 (closed)

smash/web/forms/__init__.py

+from study_forms import StudyEditForm, StudyNotificationParametersEditForm, StudyColumnsEditForm
 from worker_form import WorkerForm
 from forms import VisitDetailForm, \
     VisitAddForm, KitRequestForm, StatisticsForm, AvailabilityAddForm, \
@@ -12,4 +13,4 @@ __all__ = [StudySubjectAddForm, StudySubjectDetailForm, StudySubjectEditForm, Wo
            AppointmentDetailForm, AppointmentEditForm, AppointmentAddForm, VisitDetailForm, VisitAddForm,
            ContactAttemptAddForm, ContactAttemptEditForm, KitRequestForm, StatisticsForm, AvailabilityAddForm,
            AvailabilityEditForm, HolidayAddForm, SubjectAddForm, SubjectEditForm, SubjectDetailForm, VoucherTypeForm,
-           VoucherTypePriceForm, VoucherForm]
+           VoucherTypePriceForm, VoucherForm, StudyEditForm, StudyNotificationParametersEditForm, StudyColumnsEditForm]