- New actions, `UNPUBLISHED_ENTRY_REGISTER_DEPENDENCY` and
  `UNPUBLISHED_ENTRY_UNREGISTER_DEPENDENCY`, in
  `src/actions/editorialWorkflow.js`, with exported action creators.

- New reducers case in `src/reducers/entryDraft.js`
  for (un)registering dependencies to the current `entryDraft.entry`.

- `persistEntry` in `src/backends/backend.js` pulls dependency data
  out of `entryDraft` and saves it to metadata.

- New widget control props, `onAddDependency` and `onRemoveDependency`
  passed down to widget controls from `EntryPageHOC`. These call
  `(un)registerUnpublishedEntryDependency`.

- `RelationControl` calls `onAddDependency` when selecting a suggestion.

- New action constants in `src/actions/editorialWorkflow.js` -
  `UNPUBLISHED_ENTRY_DEPENDENCIES_REQUEST`,
  `UNPUBLISHED_ENTRY_DEPENDENCIES_SUCCESS`, and
  `UNPUBLISHED_ENTRY_DEPENDENCIES_FAILURE`, with exported thunk action
  creators.

- `loadUnpublishedEntry` returns its promise so it can be used to load
  dependencies.

- Add new thunk action `getUnpublishedEntryDependencies` to resolve
  the dependencies of a given entry.

- New action constants in `src/editorialWorkflow.js` -
  `UNPUBLISHED_ENTRIES_PUBLISH_REQUEST`,
  `UNPUBLISHED_ENTRIES_PUBLISH_SUCCESS`, and
  `UNPUBLISHED_ENTRIES_PUBLISH_FAILURE`, with exported thunk action
  creators.

- New backend and GitHub API function `publishUnpublishedEntries`.

- New reducer case in `src/reducers/editorialWorkflow.js` which
  updates editorialWorkflow state when publishing multiple entries.