Add "New X" statistics for sites, biblio, nodes, users #4901

#4901

##### Hotfix against SCHOLAR-3.10 branch

This is PR 1 of 2 (the 2nd PR will be in https://github.com/openscholar/ossap repo)

#### Changes

* Added 4 new queries to `os_stats` module
* Allow queries with count == 0 to display in stats page