Sign tweaks if needed

[ilian]

This is a feature request to fix a minor annoyance.
It would be nice if tweaks would be automatically signed if needed. This is especially useful when using LiveContainer is used in a tweak development workflow.
Every time I copy a new version of a tweak to the Tweaks directory, I currently have to navigate to the Tweaks ViewController and press the signature button at the top. Not doing so would lead to a code signature invalid error as expected.