signal sequence was finally handled

[jerch]

Inputhandler methods did not yet follow the paradigm to return true if a sequence was finally handled, thus the fallback handler get called. Fixes #1879.

[Tyriar]

What if we change it to callback: (params: number[], collect: string) => boolean | undefined and only when it's false (not undefined) will it be treated as not handled? Would save adding all this extra code to InputHandler.

[jerch]

@Tyriar Hmm yeah, tbh I dont like adding all those return values either. Guess I'd do it your way.

[Tyriar]

@jerch I made the changes, please review and merge if they look good 🙂

[jerch]

@Tyriar 👍