Add cyclic forcing support

[SouthEndMusic]

Fixes #153.

Notes:

• With timeseries which are extrapolated in a periodic manner, the first and last data values must be validated to be the same. For linear interpolations this ensures continuity, and for constant interpolation this value would be otherwise ignored.
• Time periods like years and months do not always have the same length, so this can get out of sync when these time periods are repeated. This should at least be documented well, and might need a follow-up issue.
• We add all time values in the input to the tstops. With cycling forcing this has to be expanded to all time values in all periods that fall within the simulation period.

[visr]

Suggested change

	## cyclic time series
	When cyclic forcing is set to true for a node in the Node table, every time series associated with that node in the corresponding table(s) will be interpreted as cyclic. That is: the time series is exactly repeated left and right of the original time interval to cover the whole simulation period. For this it is validated that the first and last data values in the timeseries are the same. For instance, quarterly precipitation requires giving values for every quarter at the start of the quarter, and then the value for the first quarter again at the start of the next year.
	## Cyclic time series
	When `cyclic_time` is set to true for a node in the Node table, every time series associated with that node in the corresponding table(s) will be interpreted as cyclic. That is: the time series is exactly repeated left and right of the original time interval to cover the whole simulation period. The first and last data values in the timeseries need to be the same. For instance, quarterly precipitation requires giving values for every quarter at the start of the quarter, and then the value for the first quarter again at the start of the next year.

[visr]

Looks good, but there are still some tests to fix it seems:

FAILED python\ribasim\tests\test_io.py::test_sort - AssertionError: assert ['node_id', '...condition_id'] == ['node_id', '...greater_than']
  
  At index 2 diff: 'condition_id' != 'greater_than'
  
  Full diff:
    [
        'node_id',
        'compound_variable_id',
  -     'greater_than',
  +     'condition_id',
    ]
= 1 failed, 53 passed, 1 skipped, 1 xfailed, 1 xpassed, 30 warnings in 58.63s =

Does this need to merge master?

[SouthEndMusic]

@visr this is because I did a small follow-up of #2079 where the sorting of the DiscreteControl / condition table was changed, and apparently we have 2 sources of truth for those (one in Python and one in Julia). I wasn't aware this was part of a test, will quickly fix.