We might want to iterate through the supported fingers values, to do that we
were hardcoding FP_FINGER_LEFT_THUMB and FP_FINGER_RIGHT_LITTLE as first and
last fingers.
Not that we'd ever get more fingers (unless some weird radiation would do
the job), but it's logically nicer to read than random hardcoded values.
This is a rewrite of the core based on GObject and Gio. This commit
breaks the build in a lot of ways, but basic functionality will start
working again with the next commits.
