Merge branch 'dk-issue-68-get_discussions_by_blog-v2' into 'develop'

IN clause removed as it caused serious slowdown on queries with larger result sets

See merge request !245

(cherry picked from commit 26dcbdc6)

58223097 IN clause removed as it caused serious slowdown on queries with larger result sets
971ef982 get_discussions_by_blog as sql function
5dc60144 Renamed sql file to follow naming convention
f19e0283 Rebase to current develop