Oemof-thermal

With the fourth release of oemof-thermal we have validated the compression heat pump, the compression chiller and the stratified thermal storage using data provided by the Universidad Politécnica de Madrid and the energy supplier Naturstrom AG. The results are provided in the [documentation](https://oemof-thermal.readthedocs.io/en/master/).

Besides fixing some minor flaws in the models and improving the documentation, we have cleaned the examples of the stratified thermal storage component and made it more transparent.

You can find further information on the changes made within this version of oemof-thermal in the [What’s new section](https://oemof-thermal.readthedocs.io/en/master/whats_new.html#v0-0-4-october-2-2020).

This is the third release of the oemof.thermal repository.

We introduced the absorption chiller as a new component. Within the module we provide functions to calculate, among others, the characteristic equation, the coefficient of performance and the cooling capacity. See the [documentation](https://oemof-thermal.readthedocs.io/en/latest/absorption_chillers.html) for more information.

All modules have been updated to oemof.solph v0.4.1

The documentation has been improved and the examples have been cleaned up.

This is the second release of the oemof.thermal repository.

We introduced new facade classes that simplify instantiating components. Facades for these three components are now ready to be used: SolarThermalCollector, ParabolicTroughCollector and StratifiedThermalStorage.

The documentation has been revised and extended. The repository now has function tests, and the facades are tested with constraints test.

See the [Whatsnew](https://oemof-thermal.readthedocs.io/en/master/whats_new.html#v0-0-2-2020) section for more details.

There will be a tutorial about the oemof.thermal repository at the [virtual oemof developer and user meeting](https://github.com/oemof/oemof/wiki/Meeting-May-2020-%28online%29)

This is the first release of the oemof.thermal repository. The oemof.thermal package provides tools to model thermal energy components as an extension of oemof.solph. The first release contains the following components:
* compression heat pump
* solar thermal collector
* concentrating solar plant
* thermal storage