Refactor Web Editor (3)

...s/projects/branch_defaults/_branch_names_fields.html.haml

doc/api/projects.md

doc/user/project/merge_requests/creating_merge_requests.md

doc/user/project/merge_requests/getting_started.md

doc/user/project/repository/branches/index.md

...t/repository/img/web_editor_new_branch_dropdown_v14_1.png

.../web_editor_new_branch_from_issue_create_button_v14_1.png

...repository/img/web_editor_new_branch_from_issue_v14_1.png

...oject/repository/img/web_editor_new_branch_page_v14_1.png

...ser/project/repository/img/web_editor_new_push_widget.png

...ect/repository/img/web_editor_start_new_merge_request.png

doc/user/project/repository/index.md

doc/user/project/repository/web_editor.md

doc/user/project/web_ide/index.md