LB-842: When a chained blog provider is deleted, the already selected blogs still appear on chained blog source
* chained blogs (in liveblog, liveblog-sync) filtered for having providers (or none origin_uri as legacy)
Merge branch 'liveblog-15' into lb-842-hide-orphan-chained-blogs
LB-842: When a chained blog provider is deleted, the already selected blogs still appear on chained blog source
* updating the source on re-enabling a chained blog
LB-819: On timeline all posts are 2h before CET

Use dust userdate helper for timeline dates.
LB-873: User managed banner ad on top of the blog - backend
api, model
LB-873: User managed banner ad on top of the blog - backend
* some impl. methods
LB-873: User managed banner ad on top of the blog - backend
* inser/update with type
Merge branch 'liveblog-15' into lb-873-blog-media
LB-873: User managed banner ad on top of the blog - backend
* adjusted
LB-869: On chained blogs beside the original user name also show his avatar
* starting the icon handling
Merge branch 'liveblog-15' into lb-869-chained-avatar
LB-869: On chained blogs beside the original user name also show his avatar
* some impl
LB-869: On chained blogs beside the original user name also show his avatar
* some more impl
LB-914: Media deleting should check for (FK-based) exceptions
* fixed
Merge branch 'liveblog-15' into lb-869-chained-avatar
LB-869: On chained blogs beside the original user name also show his avatar
* icon removal
LB-869: On chained blogs beside the original user name also show his avatar
* adjusted
LB-869: On chained blogs beside the original user name also show his avatar
* some upload attempts
LB-869: On chained blogs beside the original user name also show his avatar
* debug messages
LB-869: On chained blogs beside the original user name also show his avatar
* taking users