install: Use bash completion for file names
install: Use bash completion for file names

Since flatpak can now install from *.flatpak and *.flatpakref files
rather than just remotes, show those files in the bash completion of a
"flatpak install ..." command.

Fixes https://github.com/flatpak/flatpak/issues/672

handsome-feng/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak