"Swipe anywhere to Navigate" setting

[Sjmarf]

If General -> Swipe anywhere to Navigate is enabled, you can swipe anywhere on the screen to go back rather than only at the edges.

Also fixed a bug in which feed post corners weren't clipped if Swipe Actions were turned off.

Closes #130

[EricBAndrews]

Code looks good, works well!

If swipe actions are on, it may not be immediately clear that they need to be disabled for this setting to be activated--we should at least offer an explanatory footer, and possibly flip the swipe actions toggle off when swipe navigation is enabled (the same as is done when going the other way)

[Sjmarf]

Hm, I can't think of a good footer that's not too verbose. Any ideas? Alternatively we could swap out the two toggles for a single picker or something? That might not be as clear though

[EricBAndrews]

The best I can come up with for footer is "Only one of these can be active at a time"--I agree that a picker isn't as clear. We might not need a footer if they just automatically swap--that behavior should be clear enough, though you can never be too sure

[Sjmarf]

I've made both toggles enabled at all times, and turning one on turns the other off. Maybe that's clear enough without needing a footer?

[EricBAndrews]

Works for me 👍