Added simple image viewer which loads image file names
from a directory, displays the first one, then displays
the next in the list with each key press. Uses the
primitive fade front in/fade back out approach.
Also adapted Emmanuele's example code which uses Cogl
to produce a similar effect, but within a single texture.
This code loads two images specified on the command
line and cross-fades between them.
83a8d0b3bb