Remove portrait mode option (fix #535)

[Neamar]

As discussed in #535, every Android device since Lollipop has an easy way to lock / unlock rotation.

There is no need to provide such a feature at the app level anymore.

[licaon-kter]

There is no "per app Android switch"...

I would like this kept on, but then again I use Tap'nTurn, but if that becomes a nuissance (eg. gabm/TapAndTurn#38 or gabm/TapAndTurn#8 ) I'll come here asking for the toggle back.

Also, afaik, most launchers force portrait and offer a lanscape mode in settings.

[Neamar]

How often do you use landscape?

Most people I know actually never do. The only valid use case is fullscreen video, and Android is smart enough to do that for you.

I'd rather remove cruft legacy from KISS honestly.

[licaon-kter]

Reading non-mobile aware sites, pdfs. It's a usecase.

This is not, imho, cruft.

[Neamar]

Makes sense. I won't merge for now, let's wait to get more feedback on the PR!

If more people agree, I guess we can leave the setting in the app.

[CCBMhf]

I also vote to keep it in.

[nmitsou]

To me, it feels more natural to follow the system setting by default.
We could have a toggle to overpass it and lock rotation (but set to false on first run)

[Neamar]

Based on this discussion, I've reverted my previous commit.

In the end, the only thing I'm changing is the default value for new app users.