* Add migration step to remove old repo_indexer_status orphaned records
* Include RepoIndexerStatus struct definition in the migrate function
* Change .Delete(o) into ID(o.ID).Delete(new(RepoIndexerStatus))
* Simplification of the delete procedure
* Rename v91.go to v92.go
* add migration and basic UI for changing a user's theme
* update user themem
* use right text on button
* load theme based on users' selection
* load theme based on users' selection in pwa too
* update sample config
* delete older theme loading
* implement AfterLoad to set users' theme properly
* set up default theme when creating a user. This uses the installation wide theme
* use flash messages for error
* set default theme when creating a user from the cli
* fix @lunny review