Distributed Dynamic Config Store fixes

- mostly cosmetic & logging
- fixes bug dealing with root DocumentPath conversion to String
- clarification and notes around dynamic config

Change-Id: I94284f591b4045461f5121ad8318e6aa5f35fd7c
diff --git a/apps/config/src/main/java/org/onosproject/config/InvalidFilterException.java b/apps/config/src/main/java/org/onosproject/config/InvalidFilterException.java
index fcb73b0..1406b20 100644
--- a/apps/config/src/main/java/org/onosproject/config/InvalidFilterException.java
+++ b/apps/config/src/main/java/org/onosproject/config/InvalidFilterException.java
@@ -23,6 +23,8 @@
 @Beta
 public class InvalidFilterException extends RuntimeException {
 
+    private static final long serialVersionUID = 7270417891847061766L;
+
     /**
      * Constructs a new runtime exception with no error message.
      */
@@ -38,4 +40,6 @@
     public InvalidFilterException(String message) {
         super(message);
     }
+
+    // TODO add constructor with cause
 }
\ No newline at end of file