This completes an enrollment implementation for the upekts driver.
It's based on code from libthinkfinger, but as there seemed to be many
unknown details there, I spent some time analysing the bus messages in
more detail and have effectively rewritten almost all of the borrowed code.
Note that libthinkfinger is GPL licensed, so that reflects on this code too.
At release time I will ask them if they are OK for me to relicense it.
