309 no private datasets in activity streams, revisions, group listing and tag listings
make group_list_dictize reasonably fast by going through search index
[#309] add package count using search index
Merge branch 'master' of github.com:okfn/ckan into 309-package-private-everywhere
[#309] Tidy up a couple of comments

No point in putting "TODO" comments in the source code no one will
remember to go back and do them and the comment may become outdated/misleading.
Merge branch '309-package-private-everywhere'