Handle option changes while I/O Editor is running

[glutanimate]

Previously we used to block calling the options menu if an instance of the I/O Editor was running in the background. This is important since there is currently no call implemented that would update I/O Editor instances and notify them of modified settings (esp. in regards to the note type, that could leave running I/O instances in an undefined state #48).

With 32c1df07b9cb8f345967b3dd53fd39ac373d9976 this no longer works.

We should either try to restore the old functionality, or ideally implement a reset hook that would update running I/O instances. The latter approach would also resolve #48 for good.