Changing key for addresses (Bug 1470)

The addresses structure used to use the first-seen timestamp as a key.
That is not guranteed to be unique. This changes that to use an opaque
64-bit identifier. Currently, it's populated with the MAC addres
interpreted as a BigInteger, but that should not be counted on in the
future and should be checked for uniqueness.

Change-Id: I579c2c5587c62ef685317bd54049aead67406d35
Signed-off-by: Colin Dixon <colin@colindixon.com>