Add global INKHandler settings

[lazerwalker]

There are a number of options you can set on an INKHandler object, like useSystemDefault or useFallback. Right now, you need to set those individually on each INKHandler object in your app, but 99% of the time you actually just want them to apply across all INKHandler objects in your app.

We should consider perhaps creating getter/setter class methods on INKHandler that apply globally to every INKHandler object. I'm skeptical of adding in that bit of global state, but in most cases it'll save a meaningful amount of boilerplate code. I'm not 100% sure this is a good idea (or that it's not a completely-terrible "why the hell would you EVER do this?" idea), but it's worth pondering.

The old per-object properties should definitely still exist.

[pedro380085]

Right now I'm using a category that does exactly that (set the same configs to every single handler).