Write documentation and examples

[euronion]

Goal: We want a basic, but complete documentation.

Screen what is missing and suggestion implementations.

[finozzifa]

Outstanding topics:

• A easy example, e.g. manually creating a Technology and TechnologyCollection with a few Parameters, then doing currency adjustment / inflation adjustment and projection from 2020 to 2030, 2040 and 2050 and saving it as csv or json.
• An advanced example, e.g. using the DEA data
• Finalize docs/home/citing.md
• Finalize docs/home/faq.md
• Finalize docs/home/release-notes.md
• Finalize docs/home/users.md
• Review docs/user_guide/design.md
• Write docs/user_guide/datapackage.md
• Write docs/user_guide/source.md
• Write docs/user_guide/source_collection.md
• Write docs/user_guide/technology.md
• Write docs/user_guide/technology_collection.md