First attempt to of a plugin that processes climate model input data for impact models

This is a first attempt for a plugin that chews through large output of multi-dimensional model output data and creates output files that can be used for processing impact model data.

During the writing of the plugin I realised that there are many potential pitfalls I would not be able to anticipate. Like what is the correct unit of each variable - mm/h, mm/day, kg/m^2/second etc. As a possible solution I decided to create a post-processing library that allows users to do such processing by them selves and beyond.

So the plugin does the following:

1. Open all netcdf-files, get the the variables select the desired time-range.
2. Select the region according to the shapefile in the data 3a. If not instructed otherwise create a field average across the time dimension 3b. If instructed other wise, do otherwise instead.
3. Save the output data to the cloud.
4. Prepare a jupyter notebook for post-processing.

The users either download the data from the cloud or use the processed jupyter notebook to make use of the data post-processing library.

@b381718 @b381377 @g300050 if you could try and have a look?

Docs can be found here: https://www-regiklim.dkrz.de/about/climpact/