* Add ability to select different personas to generate the path to be
created.
* Move hardcoded paths to read from init's set environment.
* Add unit tests for all the utility functions that build strings to
make sure they're correct.
* Fill in persona with "0" all the time now. Will be plumbed through in
later CL.
Change-Id: I0a7f6e3640cb6b052f8823080886ee79e90b679f
Disk usage calculation will happen in more places now, so move the
installd calculation utilities out to its own library that only gets
built for the target.
Change-Id: Idceb6bd663ca6ab3d38fa00e57ee74a25b784855
