ref #7726 Move UI screenshots in the repository using git-lfs

tests/UI/expected-screenshots/Menus_user_changed.png

tests/UI/expected-screenshots/Menus_user_loaded.png

tests/UI/expected-screenshots/Morpheus_load.png

...s/UI/expected-screenshots/MultiSitesTest_all_websites.png

...nshots/MultiSitesTest_all_websites_changed_sort_order.png

...pected-screenshots/MultiSitesTest_all_websites_page_1.png

...pected-screenshots/MultiSitesTest_all_websites_search.png

tests/UI/expected-screenshots/OptOutForm_loaded.png

tests/UI/expected-screenshots/OptOutForm_opted-out.png

tests/UI/expected-screenshots/Overlay_loaded.png

tests/UI/expected-screenshots/Overlay_page_change.png

tests/UI/expected-screenshots/Overlay_page_link_clicks.png

tests/UI/expected-screenshots/Overlay_page_new_links.png

tests/UI/expected-screenshots/Overlay_period_change.png

tests/UI/expected-screenshots/Overlay_row_evolution.png

tests/UI/expected-screenshots/Overlay_transitions.png

...pected-screenshots/PeriodSelector_date_range_selected.png

...s/UI/expected-screenshots/PeriodSelector_day_selected.png

tests/UI/expected-screenshots/PeriodSelector_expanded.png

tests/UI/expected-screenshots/PeriodSelector_loaded.png