Fix #1140: [Finder] Feature request: Allow saving edited method code

[JMLF]

We set the submit callback when it's needed otherwise we unset it.

We tried changing the submit callback from the code presenter but calling whenSubmitDo: multiple times has side effects and raises an exception after the first time.

Instead what we do is :

• When a result is selected, the result stores the corresponding callback in itself (each result items has it own rules).
• We have a single submit callback in the code presenter.
• When the submit callback triggers we delegate to the result.

[estebanlm]

Sorry for the delay ;)

[MarcusDenker]

Note: I change the title to be better for the Friday mail.