added MetaContainer adaptor for ontology databases

allows for use with schema_patcher script and proper release version control

modules/Bio/EnsEMBL/DBSQL/OntologyDBAdaptor.pm

@@ -42,6 +42,7 @@ sub get_available_adaptors {
   return {
     'GOTerm' => 'Bio::EnsEMBL::DBSQL::OntologyTermAdaptor',  #deprecated
     'SOTerm' => 'Bio::EnsEMBL::DBSQL::OntologyTermAdaptor',  #deprecated
+    'MetaContainer' => 'Bio::EnsEMBL::DBSQL::MetaContainer',
     'OntologyTerm' => 'Bio::EnsEMBL::DBSQL::OntologyTermAdaptor' };
 }