Added energysystem compatibility for param_results

[henhuy]

Just a little addition to former add-node-param-obj-results PR:

Now, not only (Operational-)Model, but also the energysystem can be
given as input parameter for processing.param_results function

[henhuy]

It's only a simple feature - I did not know if I can push directly to dev...

[ckaldemeyer]

I would suggest "Model or EnergySystem" or "optimization model or energy system"

[ckaldemeyer]

If the docstring is changed, I am fine. Thanks!

[ckaldemeyer]

If the docstring is changed, I am fine. Thanks!

[uvchik]

I would say solph.model or solph.EnergySystem, because it is meant an instance of the solph.EnergySystem class and not any energy system.

By the way I would not allow passing a model but only(!) EnergySystem. Models gets their informations from the EnergySystem so this is the source. Models might vary in the future so it will be additional work to keep both APIs in line. So I would not add the option to pass an ES but replace the option to pass a Model.

[henhuy]

By the way I would not allow passing a model but only(!) EnergySystem.

I thought I shouldn't change the API after a release?
That's the only reason I allowed both options...

[uvchik]

Ah okay, I did not know that this is already part of v0.2.0, I thought this is something new.

Anyhow, we should talk about the usage of Models and Systems on the next developer meeting.