Naming conflit in expose observation setup

[valeriof7]

There is a naming conflict in the tudatpy/tudatpy/kernel/expose_numerical_simulation/expose_estimation_setup/expose_observation_setup.cpp file between the observable type objects and the names of the Python functions used to create the associated observation model and define its settings. For example, the object for the dsn n-way range is usually called as follows

tudatpy.numerical_simulation.estimation_setup.observation.dsn_n_way_range

While the associated observation settings are (currently) created using

tudatpy.numerical_simulation.estimation_setup.observation.dsn_n_way_Range(
                    current_link_definition, light_time_correction_list
                )

I think a refactoring of the naming for the observation settings (e.g. using something like create_n_way_range or n_way_range_settings) should be done.

[DominicDirkx]

In line with (most) of the other entries of the ObservableType enum, I propose we name the entry there. Proposed correction pushed to feature branch:
8d3d947