Track if a package is system-installed with root-relative installed files vs. plain package

[pombredanne]

Track if a package is system-installed with root-relative installed files vs. plain package.
For instance a Debian installed package file paths are rooted in a rootfs. But when you extract a .deb the files are rooted in the package archive. We should be able to accommodate for these cases

[pombredanne]

In particular in SCIO, we track a rootfs_path for resources