User shortcuts customization

[aberkl]

With respect to #652 and #653: I believe LosslessCut cut benefit very much from "User shortcuts customization".

Ideally this would have an entry in "Settings" but a (text, json, ...) config file would be sufficient as well.

Compare to screenshots from DJV View and kdenlive.

[markusd1984]

I think that's one of the longer nice to have features being considered, certainly offers a lot of flexibility for the fastest personal use of LC who like using shortcuts.

A mapping feature would make this the most user friendly, even if that writes it to a local settings file if they feature also gets implemented.

[mifi]

thanks for your suggestion. I referenced this issue in the main keyboard shortcuts issue. Need to close some issues (too many)