Update tutorial on how to upload data

[stap-m]

The tutorial https://openenergy-platform.org/tutorials/8/ needs an update:

• First sentence; "... two different paths may be selected."
• Start both section headlines with "The users who ..." and unify singular / plural
• Section 1: "... The sandbox is not visible. The upload process is very fast but beware, the sandbox gets deleted regularly. Once accustomed to the sandbox the user may use the model draft and upload real project data" (delete its !)
• Section 2: "... which is very intuitive and provides good support for all mandatory fields.""
• Final sentence: "As soon as the data is finalized and the user makes no further changes, the data can be permanently stored at the corresponding topic. There, the stored data becomes visible to others. The upload process takes some time and ..."" Question: topic or schema? Question: "and the data is stored in GitHub." really??

This is important for the PtJ link list!

[christian-rli]

I implemented the changes. Stored on GitHub are the metadata and their evolution - I changed the description accordingly.