Features/#857 store intermediate results of heat demand timeseries

[ClaraBuettner]

Fixes #857 .
Fixes #950

Before merging into dev-branch, please make sure that

• the CHANGELOG.rst was updated.
• new and adjusted code is formated using black and isort.
• the Dataset-version is updated when existing datasets are adjusted.
• the branch was merged into the
  continuous-integration/run-everything-over-the-weekend-branch.
• the workflow is running successful in test mode.
• the workflow is running successful in Everything mode.

[nailend]

This column does not exist as described in the database as the table is exported with different columns here. Please adapt the class definition accordingly. Just to mention: If you use pd.to_sql with if_exists=replace pandas will choose the datatype of the columns by itself and not stick to your definition. Thats why they end up without PK defined. You might also have to define the dtypes explicitly.

You can use this to not hardcode all of them :

dtypes = {column.key: column.type for column in EgonDailyHeatDemandPerClimateZone.__table__.columns}

[ClaraBuettner]

Most of the commits from this feature branch were already merged into dev (see #950), theses are not visible in this PR anymore. I don't really know how to deal with this, there were several commits and it is not really possible to find all of them again.