The old approach of including the same source files into
multiple places is less than pretty.  But moving the code
to libply didn't seem right either, since libply is fairly
generic and could in theory get swapped out with a standard
runtime at some point.

Also, exposing libplybootsplash as an external library will
facilitate creating out of tree splash plugins.

Previously we've just hard coded the location to the fedora
logo.  Now it's a configure time flag.  We also have a configure
time flag for a background color that goes with the logo, but
none of the splash plugins make use of it yet.

Just makes things more consistent.

The idea is to make a plugin that matches mockups done by
Mike Langlie.  The mockups feature a throbber that spins
in the shape of an infinity sign.  This is just a placeholder.
Most of the mockup isn't implemented yet.