Changed the default fields, making slides without text possible too.

Hello,

I very much like the way this bootstrap carousel is build. It has quite some features, but not too much hard-coded like the others I've encountered so far.

I've got a little issue with the default showing of text on the slides. Because these values are default in the xml, they can't be removed in the module. I also added a check for the default versions, if for some reason you don't want to get rid of those.

Hope you can implement this.