add full list of BMC URL-s

Adds the full list of BioMedCentral journal URL-s to the BMC plugin.
These are imported from a separate, new
openarticlegauge/plugins/resources directory.
add list of Elsevier journal URL-s

We do not yet have an Elsevier plugin, but we do have a list of journal
URL-s, stored under openarticlegauge/plugins/resources/