EE: Introduce ApplicationSettingImplementation
requested to merge ee-47491-gitlab-fakeapplicationsettings-doesn-t-respond-to-all-the-methods-applicationsetting-responds-to-itself into master
EE for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25803
No EE specific changes. Just want to see EE tests.
Edited by Lin Jen-Shin