Button that comes with the popover mixin. Essentially only difference between this and FwPopoverIcon is that the tagName is button rather than i.
container
UnknownContainer for the popover, set to 'body' to prevent parent styling from modifying the popover
placement
UnknownPlacement of the popover (top, bottom, left, right, or auto) auto is a special placement which will appear top or bottom based on location on the screen