Issue #256: Remove per-user theme support.
Issue #256: Remove per-user theme support.
Issue #1493108 by marcingy, sun, Mike Wacker, kbasarab, Berdir, Rok Žlender, cosmicdreams, alexpott: Convert logging and error settings to configuration system.
Issue #1714462 by n3or, sun, Gábor Hojtsy: Convert language negotiation settings to configuration system.
Merge with 1.x
Merge branch '1.x' of github.com:backdrop/backdrop into 1.x
Issue #1496534 by cosmicdreams, alexpott, aspilicious, kim.pepper, acrollet, dagmar, beejeebus, wizonesolutions | heyrocker: Convert account settings to configuration system.
Merge pull request #374 from quicksketch/hellomrcat-170-account

Issue #1496534 by cosmicdreams, alexpott, aspilicious, kim.pepper, acrollet, dagmar, beejeebus, wizonesolutions | heyrocker: Convert account settings to configuration system.
Merge pull request #361 from hellomrcat/170-lang

Issue #1714462 by n3or, sun, Gábor Hojtsy: Convert language negotiation settings to configuration system.
Issue #1757566 by alexpott, aspilicious: Convert user account e-mail templates to configuration system.
Issue #1496534 by cosmicdreams, alexpott, aspilicious, kim.pepper, acrollet, dagmar, beejeebus, wizonesolutions | heyrocker: Convert account settings to configuration system.
Merge pull request #355 from hellomrcat/170-email

Issue #1757566 by alexpott, aspilicious: Convert user account e-mail templates to configuration system.
Issue #1496534 by cosmicdreams, alexpott, aspilicious, kim.pepper, acrollet, dagmar, beejeebus, wizonesolutions | heyrocker: Convert account settings to configuration system.
Merge pull request #375 from quicksketch/hellomrcat-170-error

Issue #1493108 by marcingy, sun, Mike Wacker, kbasarab, Berdir, Rok Žlender, cosmicdreams, alexpott: Convert logging and error settings to configuration system.