Merge branch 'release-0.26.0' into fix-4909, add commentary

.gitignore

OSX/Metabase.xcodeproj/project.pbxproj

OSX/Metabase/Backend/MetabaseTask.m

OSX/Metabase/Backend/ResetPasswordTask.m

OSX/exportOptions.plist

...eb-docker/.ebextensions/metabase_config/metabase-setup.sh

bin/ci

bin/config.json

bin/docker/run_metabase.sh

bin/osx-release

bin/osx-setup

bin/version

circle.yml

docs/administration-guide/01-managing-databases.md

docs/administration-guide/10-single-sign-on.md

docs/administration-guide/images/authentication.png

docs/administration-guide/images/field-options.png

docs/administration-guide/images/large-db-toggle.png

docs/administration-guide/images/ldap-attributes.png

docs/administration-guide/images/ldap-form.png