LB-855: Delete the population of root user
* root user not populated
LB-863: After a blog is closed it should disappear from Live Blog menu
* isOpen filter parameter for blogs
LB-860: On Manage Collaborators -> add new collaborators, it is showed only first 20 collaborators.
* limit-filter added
LB-545: Embed URL crashes if a user who has published posts is deleted
* db upgrade adjusted
Merge pull request #278 from msat-cont/lb-545-user-retirement

LB-545: user retirement
Merge pull request #270 from msat-cont/lb-863-filter-closed-blogs

LB-863: filter closed blogs
Merge branch 'liveblog-15' into lb-860-limits-for-collab-list

Conflicts:
	plugins/livedesk/livedesk/impl/blog_collaborator.py
Merge pull request #271 from msat-cont/lb-860-limits-for-collab-list

LB-860: limits for collab list
Merge pull request #262 from msat-cont/lb-855-root-not-wanted

LB-855: root not wanted