Project page update

Hi all,

I realised with the update I posted earlier that people who could've purchased the premium version (nobody has yet luckily) wouldn't be able to download the update without paying for it again.

With that in mind, I've decided to update the project page from a donation style page where I set a custom price for the premium version to a paid project page where the purchase gets you the premium version and the Free version is marked as a "Demo" (I can't change the terminology unfortunately)