* the entrypoint iterator's order is not defined and changes when
  packages are installed with/without the '--editable' flag
* thus, we cannot rely on the invenio-cache extension being initialized
  for our view function decorations

* use DOIs defined in the metadata only as a fallback if the record has
  no managed PIDs

* also, remove the LOCAL_LOGIN_ENABLED configuration variable, because
  that's now part of Invenio-Accounts

* previously, some javascript snippet from invenio-theme would fail
  because our header doesn't follow the expected structure (i.e.
  expected elements were missing)

*) typo fixed

* add alt text for logos, hidden labels for search controls

* this resulted in invalid html and thus in weird visuals

* override the header template from invenio-app-rdm to make the search
  button orange
* fix the wrong text color on the login button

* removed trailing whitespaces
* also, hide staging warning per default

staging banner to page template

* add links to the cards on the frontpage
* have the "learn more" link point to the roadmap of Invenio RDM