UUID revamp

Previously, ::create tried hard to convert everything to binary (and hex)
We usually use alphaDecimal throught the code, though.
The only place that actually needs binary is DB. Hex is almost non-existant.

Instead of trying to force everything to binary, then re-converting to
alphanumeric when needed, I changed this so that the object can be built
from an alphanumeric string (or binary, or hex), and only converts when
needed.

In theory, this should change things around so that only when read/written
from/to db, a conversion would have to be done from/to binary (which is
already the case). All other usages (internal, or when fetched from cache)
should be able to just get by using the alphanumeric version, which now
no longer needs to be converted to binary to build the UUID object.

Change-Id: I60e7cd6ef6cad73d11f15473c70261ae41e908d3
Merge "UUID revamp"