Improved touchscreen menu control

[Legion2]

Added openOnHover option, which is enabled by default for backwards compatibility. When the option is disabled, the menu does not open on hover, this is useful for touchscreens, where "hovering" is only emulated. So this should finally fix #13.

The refactoring of the open/close menu javascript and css handling now make it also possible to add logic to reliable close the menu. e.g. close the menu after 5 seconds or close the menu after press of a menu item.