Update input_data.rst

- Added at the beginning how the three sectors are treated by Deflex: Power is regional, mobility is global and heating is partly regional (heat plants and CHP) and partly global (decentralized sources).
- Added on most of each section a table that shows the framework of the input data set. (demands has only one example since we want to split each sector) (storages does not have a framework since we also want to make some changes here).