Allow instance of Livetime for livetime property

[martwo]

The livetime property of the DatasetData class should allow to be an instance of core.livetime.Livetime. So derived Dataset classes can construct a Livetime instance if e.g. good-run-list information is available.

skyllh/skyllh/core/dataset.py

Lines 2822 to 2828 in 074c508

	@livetime.setter
	def livetime(self, lt):
	if lt is not None:
	lt = float_cast(
	lt,
	'The livetime property must be castable to type float!')
	self._livetime = lt