Update Xref.java
Update Xref.java

Added identifier for Primary id's
bridgedb/BridgeDb,bridgedb/BridgeDb,bridgedb/BridgeDb,bridgedb/BridgeDb,bridgedb/BridgeDb,egonw/BridgeDb,egonw/BridgeDb,egonw/BridgeDb,egonw/BridgeDb,egonw/BridgeDb