Currently all the privdata is written into a single encrypted file.

This makes it more likely that, if multiple people are co-administering
with propellor, they will make conflicting changes to the privdata.
And resulving such a conflict would be pretty tricky.

This could be improved by splitting up the privdata file, so there's one
encrypted file per item. Conflicting commits would then be less likely,
and even if they happened, it would only be one item in conflict, so
should be eaiser to resolve it.

Are there privacy concerns with splitting privdata? It would let anyone who
can access the repository but not decrypt it guess more about its
properties. 

They could look at the size of an item and make guesses about eg, the
length of a password. This could be blocked by padding the privdata, but it
would need to be padded before encryption with binary garbage.

They could also enumerate the various privdata fields. However, this can already
be done by looking at the propellor configuration, so I don't think it's a
problem.

Finally, an attacker could look at the history of what privdata changed
when. Currently, all an attacker can see is that some change was made to
the privdata file; splitting it up would let them see which fields were
changed when.
