Add a concept of rating confidence to each application

The idea is that if a 30 number of people have rated an application at 80% it is
prefered over an application rated at 100% by just one person.

It will allow us to filter out spurious results when choosing picks automatically.
fedora-tagger: Update to a new version of the tagger API to provide ratings confidence
Do not set the application state in the loader

If we have two plugins that want to be run on install, the second has to process
a patch with the 'wrong' state. Rely on the plugin to do the right thing itself.
fedora-tagger-usage: Add a plugin to collect install/remove data

This is disabled by default at the moment. To enable, use:

$ gsettings set org.gnome.software enable-usage true