config: no longer take named calendars from (maybe null) scheduler
config: adding a few setters
Merge remote branch 'origin/master'

* origin/master:
  config+ui: migrated Task and TasksModel to SharedUiItem framework

Conflicts:
	libqron/config/schedulerconfig.cpp
	libqron/config/step.cpp
	libqron/config/step.h
	libqron/config/task.cpp
	libqron/config/task.h
config+ui: migrated TaskGroup, TaskGroupsModel and TasksModel to SharedUiItem framework