Add featured data based on new mockups

The images are still temporary, and need to be replaced.
The featured.ini file contains more data for the featured
graphics: various colors, as well as the title and subtitle
to display in the tile. This data will be read by the
hardcoded-feature plugin in the future.
Read data from featured.ini

The hardcoded-feature plugin now returns more data for the
featured app as generic metadata items. It reads this information
from the featured.ini file, making it no longer truly hardcoded...
Implement better featured graphics

Instead of just a big image in a standard button, we show an
image, title and subtitle with custom css that renders a gradient
that makes it appear seamless. The stock button style is gone.