Allow free Presenter users to purchase single backgrounds

So, it's Christmas right now and although Worship Extreme have kindly made 3 Christmas motion backgrounds free, I might like the option to purchase one of the ones listed as only available to paid users. We are small congregation and its not viable for us to pay £15 p/m when we use a very basic set up for only one service per week.

Thanks for your consideration!

Graphics can be purchased from Graphics in Motion directly: https://graphicsinmotion.com/collections/motion-graphics

These can now be purchased directly within WorshipTools.