Make them consistent with general upgrade instructions.

youtube-dl has been removed, and in-place import and federation probably deserve mention.

Rename occurences of the file through the documentation.

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

typo

[doc] Installation: moved wheel installation earlier in the process so we don't require build-essential

[doc] Arch Linux installation: modified the command for user creation so it works on both Debian and Arch