Refactored structure of observable_mixins. Ensemble_mean is now calculated individually.

imagine/__init__.py

...ne/likelihoods/ensemble_likelihood/ensemble_likelihood.py

imagine/magnetic_fields/galmag_field/__init__.py

imagine/magnetic_fields/galmag_field/galmag_field.py

imagine/magnetic_fields/galmag_field/galmag_field_factory.py

imagine/observables/__init__.py

imagine/observables/observable.py

imagine/observers/hammurapy/hammurapy.py

imagine/observers/hammurapy/model_mixins/galmag_mixin.py

imagine/observers/hammurapy/model_mixins/jaffe13_mixin.py

imagine/observers/hammurapy/model_mixins/jf12_mixin.py

imagine/observers/hammurapy/observable_mixins/dm_mixin.py

imagine/observers/hammurapy/observable_mixins/dust_mixin.py

imagine/observers/hammurapy/observable_mixins/ff_mixin.py

imagine/observers/hammurapy/observable_mixins/mixin_base.py

imagine/observers/hammurapy/observable_mixins/rm_mixin.py

imagine/observers/hammurapy/observable_mixins/sync_mixin.py

imagine/observers/hammurapy/observable_mixins/tau_mixin.py