Update loaded lua script on every run

[vadosnaprimer]

If you've loaded a script once, editing the file won't take any effect until you pick that same file again through the menu.

When writing a script it's very often that you have to edit and reload it a lot of times, and there's no intuitive benefit in it not updating in libtas memory after you've edited the script and saved the changes.

Ideally there'd also be an indication of which script is currently loaded, to make it obvious that there is one, and which exactly (makes sense when juggling several scripts).

[clementgallet]

Not what you asked (yet), but in d050a1a lua print() output is redirected to its own console in a Qt window