use POST for on/off/toggle/action/presets

the old entry points are still present, but on/off/toggle already emit
a deprecation warning in the debug log. However, menu.json was changed in
an incompatible way (now returns a list of hashes, not a list of lists)
fix actions and presets in mobile template
mobile-mail: Use POST /action for everything
remove /m/{actions,presets}
re-add support for blinkencontrol and charwrite in mobile overview
Merge remote-tracking branch 'origin/post-actions'

Conflicts:
	templates/mobile-main.html.ep