Make auth_method_picker layout work in landscape

[samtstern]

Issue #522

Landscape:

Portrait:

[samtstern]

@SUPERCILEX take a look if you can. I chose not to go full ConstraintLayout since this was easy enough to solve the "normal" way and the addition of buttons at runtime makes things a little strange.

[SUPERCILEX]

@samtstern LGTM! Though isn't there a way we can use the include tag to do less copy pasting?

PS: I'm looking into the manifest thing for #559 so the Travis build will be happy after that.

[SUPERCILEX]

@samtstern Looks like you need to merge from 1.2 dev to make the Travis builds pass.