Rename userscripts to qutescripts

[The-Compiler]

To avoid confusion with Greasemonkey userscripts.

See #5999 and #6022.

[toofar]

Updating references in docs and commands help, and moving the folder, seem easy enough. What are the backwards compatibility requirements?

1. help packagers notice the change in case anyone is packaging the qutescripts, maybe nothing required? Hopefully the changelog entry and the old directory missing are enough
2. migrate existing installations userscript folders somehow? Or support the old name for a bit and log a warning (or show a message)? Add a new migration mechanism to move the not-system ones?
3. support old bindings/aliases for spawn --userscript and hint userscript just drop the old names? Or support both?