Minimal functionality completed.

Fromage works for it's intended purpose; it can record video while the
user watches herself in a Gtk application. Numerous items remain to be
done:

• Right now the pipeline assumes video/x-h264 as video source media
type; this should be dynamic depending on the capabilities of the
system.
• The application tries to select the "best" parameters for the
sources, but there is no way to override them.
• There is no V4L2 controls settings; which is one of the reasons for
writing Fromage in the first place.
• No filters; no photographs; no facial recognition for doggy ears.