Improvements to package and supervision scripts.

Make `package-install` and `package-remove` work properly; don't freak out
during installation/removal/supervision if a package has no services; rework
default logging code to work well for interactive use; provide completion
messages for start/stop/install/remove operations to make success obvious.

This also adds an `info` logging target for the default logging implementation;
I'll rework the non-interactive logging code in `include/logger` to support this
in the next commit.