Merge in the new PBING code

Remove old pc-metapkgmanager, will be replaced by "pbi" commands

Add new 'pc-pkg' command, used by AppCafe or other processes that need
to install / upgrade packages, and want to use the libsh/ conflict
detection / removal
Don't need to populate /usr/pbi anymore
Goodby to the old pc-pkgmanager, its functionality is now being merged
into the AppCafe

While here, fix up system-updater-tray only show pkg / pbi updates
via pbing