Candidate volumes for packages, fix symlink.

Add API to determine the possible candidate volumes that a package
can be moved to.  For example, it currently knows that we need to
move ASEC-based apps through internal storage before migrating them
to a private volume.

Comparator for consistent VolumeInfo ordering when displayed in UI.

Fix native library symlink to be volume UUID aware.

Bug: 19993667
Change-Id: I68d5fac5f0f776ac1c7dd15e7a984bfe2704f3f7