Merge branch '233568-create-epic-from-boards' into 'master'

app/assets/javascripts/boards/components/board_list.vue

...ssets/javascripts/boards/components/board_list_header.vue

app/assets/javascripts/boards/components/board_new_issue.vue

app/assets/javascripts/boards/constants.js

ee/app/assets/javascripts/boards/boards_util.js

...p/assets/javascripts/boards/components/board_new_epic.vue

...s/javascripts/boards/graphql/epic_create.mutation.graphql

ee/app/assets/javascripts/boards/stores/actions.js

...avascripts/graphql_shared/fragments/epic.fragment.graphql

ee/spec/frontend/boards/boards_util_spec.js

ee/spec/frontend/boards/components/board_list_header_spec.js

ee/spec/frontend/boards/components/board_list_spec.js

ee/spec/frontend/boards/stores/actions_spec.js

locale/gitlab.pot

spec/frontend/boards/board_list_helper.js

spec/frontend/boards/board_list_spec.js