removed person Pid type, relying on the List of StructuredProperty defined in the common OafEntity superclass

src/main/java/eu/dnetlib/dhp/schema/oaf/Pid.java

@@ -1,31 +0,0 @@
-package eu.dnetlib.dhp.schema.oaf;
-
-import java.io.Serializable;
-
-public class Pid implements Serializable {
-    private String schema;
-    private String value;
-
-    public String getSchema() {
-        return schema;
-    }
-
-    public void setSchema(String schema) {
-        this.schema = schema;
-    }
-
-    public String getValue() {
-        return value;
-    }
-
-    public void setValue(String value) {
-        this.value = value;
-    }
-
-    public static Pid newInstance(String schema, String value){
-        Pid pid = new Pid();
-        pid.schema = schema;
-        pid.value = value;
-        return pid;
-    }
-}