Set system package flag on OS packages.
HaikuDepot: Clean up some aspects of package handling.

- A package can potentially be installed in more than one location. As
  such, track all of them on PackageInfo (not yet exposed/used).

- Rather than attempting to use location, check the package's flags to
  see if it's a system package. If so, disallow deinstallation. Not quite
  complete yet though, as we still needs to also resolve the deps of any
  system package, and likewise disallow removal of those.
Fix permission of text file within zipfile.

LICENSE.marvell-firmware.txt was mistakenly marked as an executable.