Rewrite

Feature complete prototype, which hopefully won't need much more changes and polishing and won't differ much from final release.

Package builds (see mm-dev-detect) and it runs fine on mox and omnia.

However note that:

• notifying users is done using original script from pakon-dev-detect - I could use new notification system, but I guess dev-detect will be shipped sooner than notification-system, so for compatibility reasons I decided to use this legacy script
• There could be timestamp when device first or last appeared to be able clean up database later, but it is not necessary at this stage.