Fixed broken video downloads and added descriptions for file formats

Hi,

Some video portal downloads were not working for some time, we've fixed them now and everything should be working again, however we've limited the support for the video portals but have most of the popular ones.

Also on the Supported Formats page, we've now added description about different file formats and their general uses, we hope that this information would be useful to our users.

Thanks,

FreeFileConvert