Carousel file format
--------------------

Plain text file, type &fff
          
First line: 100 <interval in csec>
Subsequent lines: <C|S|T|F>[C] <filename>

100 is the file version number.
For each file, the first letter gives the scale of the image:
 C = centred
 S = scaled
 T = tiled
 F = fullscreen
There is an optional C for caching JPEG images.

The backdrops are then used in the order listed in the file.

For example,
100 2000
C SDFS::Pine64.$.Images.Backdrops.PineBook.PineBcyan
S SDFS::Pine64.$.Images.Backdrops.PineBook.PineBgreen
T SDFS::Pine64.$.Images.Backdrops.PineBook.PineBred
