Use "Installed package" instead of "Installed Package".
This ends up saving a surprising number of bytes.
Don't spew warnings when there are no matches. Also, use the string builtin instead of calling sed. Fixes #3949
* Added FreeBSD's pkg to __fish_print_packages * Portmaster completes on installed packages and ports * Options list as per fish_generate_completions, needs to be tidied up further but will suffice for now
