initial ui for entry filtering

src/main/java/com/commafeed/backend/feed/FeedEntryFilter.java

@@ -56,6 +56,7 @@ public class FeedEntryFilter {
 		};
 
 		JexlEngine engine = new JexlEngine(uberspect, null, null, null);
+		engine.setStrict(true);
 		engine.setClassLoader(cl);
 		return engine;
 	}

src/main/java/com/commafeed/backend/model/FeedSubscription.java

@@ -41,6 +41,6 @@ public class FeedSubscription extends AbstractModel {
 	private Integer position;
 
 	@Column(length = 4096)
-	private String filter = "author.contains('a')";
+	private String filter;
 
 }