add long keys to all entities

src/main/java/com/commafeed/model/AbstractModel.java

@@ -0,0 +1,26 @@
+package com.commafeed.model;
+
+import java.io.Serializable;
+
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.MappedSuperclass;
+
+@SuppressWarnings("serial")
+@MappedSuperclass
+public abstract class AbstractModel implements Serializable {
+
+	@Id
+	@GeneratedValue(strategy = GenerationType.AUTO)
+	private Long id;
+
+	public Long getId() {
+		return id;
+	}
+
+	public void setId(Long id) {
+		this.id = id;
+	}
+
+}