Annotate the install counts onto the queryset vs. count method.
Annotate the install counts onto the queryset vs. count method.

This removes the giant increase in queries fired off by using the
`count` method and instead uses annotation to add them in.

Also, this allows us to restore the "source" for the install_count
field so that we can sort by install_count in the datatable now.

salopensource/sal,salopensource/sal,sheagcraig/sal,salopensource/sal,salopensource/sal,sheagcraig/sal,sheagcraig/sal,sheagcraig/sal