Improve Examining Data on the NCBI SRA Database episode

[Czirion]

Reviewer's comments:

1. the SRA-Run section might need to be slightly restructured, mostly because it currently tries to address both the new and the legacy SRA-Run tool.
   2)Examining Data on the NCBI SRA Database can be a little overwhelming. There is too much information on the screen, but I don't know if there is something to do about it other than taking it slow and making sure everyone follows. I didn't really get the reason of using the "old RunSelector" instead of the new one, I imagine the old one will become deprecated at some point...

To do: Improve the sequence of steps and remove confusing mentions to the old run selector.

[Czirion]

There is now only one flow of steps without the Old Run Selector