NavigationDrawer - visibility API

[anezthes]

Quote from developer:

Any solution that makes setVisible impact the visibility is fine. So calling hide on false, show on true is good. isVisible should of course reflect the visibility, so after calling hide directly isVisible should return false, and vice versa. (btw: Don't fully get the DOM-animation slide in/out problem) To me the best solution would be to remove show/hide/toggle because it is redundant (and forces app-developers to know about that) and instead override the setVisible/isVisible to behave as needed for NavigationDrawer