Unit tests for some Intent objects and compilers

Unit tests for HostToHost and MultiPointToSinglePoint intents
and intent compilers.

Made Intent classes final to make them immutable.
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/MultiPointToSinglePointIntentCompiler.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/MultiPointToSinglePointIntentCompiler.java
index 68c55dd..aecd3ba 100644
--- a/core/net/src/main/java/org/onlab/onos/net/intent/impl/MultiPointToSinglePointIntentCompiler.java
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/MultiPointToSinglePointIntentCompiler.java
@@ -37,7 +37,7 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected PathService pathService;
 
-    private IdGenerator<IntentId> intentIdGenerator;
+    protected IdGenerator<IntentId> intentIdGenerator;
 
     @Activate
     public void activate() {