In Python, simplify simulation initialisation

[fpagnoux]

Fixes #726

In Python, simplify simulation initialisation:

Before:

simulation = ...
holder = simulation.persons.get_holder('salary')
holder.set_input('2018-08', [4000])

Now:

simulation = ...
simulation.set_input('salary', '2018-08', [4000])

[bonjourmauko]

Hi @fpagnoux, I have just one question about scope: is this just about scenario initialisation or set_input in general? For example in scenarios.py:

        if test_case is None:
            if self.input_variables is not None:
                # Note: For set_input to work, handle days, before months, before years => use sorted().
                for variable_name, array_by_period in sorted(self.input_variables.items()):
                    holder = simulation.get_variable_entity(variable_name).get_holder(variable_name)
                    entity = holder.entity
                    for period, array in array_by_period.items():
                        if entity.count == 0:
                            entity.count = len(array)
                            entity.ids = range(entity.count)
                        holder.set_input(period, array)

Should this be refactored to the following?

        if test_case is None:
            if self.input_variables is not None:
                # Note: For set_input to work, handle days, before months, before years => use sorted().
                for variable_name, array_by_period in sorted(self.input_variables.items()):
                    entity = simulation.get_variable_entity(variable_name)
                    for period, array in array_by_period.items():
                        if entity.count == 0:
                            entity.count = len(array)
                            entity.ids = range(entity.count)
                        simulation.set_input(variable_name, period, array)

[bonjourmauko]

=> Example

[bonjourmauko]

There's just :

• one typo that'll fix myself.
• cleanup to be done that do not block the PR.

Good job!