logfs: support multiple instances of logfs
flashfs: use uintptr_t instead of uint32_t in flashfs API
ut logfs: add support for testing a 2nd partition
logfs: load/save UAVOs to specific logfs partition

Now that multiple filesystem partitions are supported,
the UAVO manager needs to be specific about which partition
to load/save its objects to.
Merge pull request #457 from solidgoldbomb/logfs-multi-instance

logfs: support multiple instances of logfs