Fix redirection on config editor
Issue #2397737 by joshtaylor: SchemaIncompleteException: Schema errors for devel.settings with the following errors: devel.settings:error_handlers.1
Replace drupal_strtolower by the unicode library
Fixed typo on devel schema
Issue #2398995 by willzyx: Route definitions in devel.routing.yml uses _content instead of _controller in 'defaults' section
Issue #2385973 by joachim: Mail logger is broken