* 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