keyboard-only interactions need menu button fallback for mobile

[hannesstruss]

Tapping the area below the last rule just focuses it, and doesn't pop out the keyboard.

https://www.youtube.com/watch?v=089Qcb12lhQ&feature=youtu.be

[forresto]

I think I have to add an "add paragraph" button, since node selections hide OSK. Delete as well, since keyboard is only way to delete selected hr.

[forresto]

(@hannesstruss the original hr issue is fixed with v2 work)

[forresto]

(dragging blocks doesn't work on mobile, so we need move up, down menu buttons)