[#2528] Fix is_child_indicator() and is_child_period()
[#2528] Fix is_child_indicator() and is_child_period()

The methods checking if an indicator or period is a child in a results framework should now use the FKs to parent indicator/period objects.

akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr,akvo/akvo-rsr