accounts: login template allow set title
accounts: login template allow set title

* Allows child templates to override the title of the login
  page.

Signed-off-by: Javier Martin Montull <ea6b80e26c65acc242d8916fb6eefa01b123cb69@cern.ch>
Reviewed-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio-accounts,inspirehep/invenio-accounts,inveniosoftware/invenio-accounts,inveniosoftware/invenio-accounts,tiborsimko/invenio-accounts,inspirehep/invenio-accounts,tiborsimko/invenio-accounts,inveniosoftware/invenio-accounts,inspirehep/invenio-accounts