Autorefresh, invalidate and hidden container

See #239 and #147. There are currently two things I'm missing:

First would be an option `autorefresh` to disable/enable the corresponding plugin. 

And the second thing is that I'm not happy with is a part of the second commit which just suppresses `refresh` during initialize. Because whenever a carousel is hidden after initialize and `update` is called it will update nevertheless. So either `update` always ignores if the element is visible or not, even during initialize. Or we check always for visibility within `update`. The second approach would slow down the `update` because checking for visibility costs time.