* 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
* prevent pull request to be merged when PR is a WIP
* add tests
* add helper to prepend WIP: in PR title
* move default wip prefixes into settings
* use configurable WIP prefixes in javascript and default to first one in templates
* add documentation
* add unit test on pull model
Signed-off-by: Julien Tant <julien@craftyx.fr>