Generalize Downloader

[liellnima]

Requests to extend the downloader for more internal (and later external) use cases.

• project tag in configs: generalize downloader to be able to retrieve data from cmip6, cmip6plus, e3sm, input4mips, and if possible more.
• get rid of look up tables: especially for "scenarios" and "models" we are limiting ourselves with the lookup tables (especially for input4mips) - those lists seem to be narrowed down to our core dataset, and hence the code blocks to downloads any data that is outside of our current core dataset. Finding a new way to handle this rather general problem would be great. It would give us more freedom and make the code base probably smaller? (when getting rid of the lookup tables)
• add more optional specs to configs: ensemble member number that is downloaded, temporal frequency, nominal resolution. we might want to extend that further upon requests or find another way how people can extend this themselves.
• adapt input4mips: unintuitive behavior: input4mips currently downloads every experiment of the desired variable. We might want to separate between downloading specific ssp scenarios or historical data.

Testing config files can be found in "downloader" for all those cases.

[liellnima]

Adding more information: Dependency on selected scenarios must be removed