Make overdimensioning factor for heating systems specific to central/decentral heating

[amos-schledorn]

Currently, the factor overdimension_individual_heating = 1.1 is applied to both central and decentral heating for adequate investment decisions at heat demand above model input. This disadvantages CAPEX-heavy technologies like heat pumps and is probably not necessary, at least for central heating, due to heat storage and the possibility to invest in inexpensive boilers.

Changes proposed in this Pull Request

• The config setting sector/overdimension_individual_heating is renamed to sector/overdimension_heat_generators made heat-system specific allowing to set different values for central and decentral heating:

 overdimension_heat_generators: 
    decentral: 1.1  #to cover demand peaks bigger than data
    central: 1.0

• It defaults to 10% overdimensioning for decentral and none for central heating

Checklist

• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Changed dependencies are added to envs/environment.yaml.
• Changes in configuration options are added in all of config.default.yaml.
• Changes in configuration options are also documented in doc/configtables/*.csv.
• A release note doc/release_notes.rst is added.

Testing

In a simple test case (Germany, 1 node)

scenario:
  clusters:
  - 1
  planning_horizons:
  - 2030
countries: ['DE']

Urban central heat mix increases in favour of heat pumps:

Master:

Feature:

[nworbmot]

Looks good to me! Perhaps @lisazeyen should also double-check. It was stupid before that it was called overdimension_inidividual_heating then applied also to district heating (my fault).