Refactor connectivity intent creation to use builders

- Each connectivity intent now has only one constructor
- Intent constructors are now private for leaf classes and
  protected for classes that can be derived from
- Each intent class has a Builder class that accumulates
  parameters for intent creation
- Each intent class has a public static builder() method
  to create a builder
- Each Builder class has a build() method to create the
  intent from the accumulated parameters
- Added keys to a few intent types that were missing them
- Tightened up usage of checkNotNull(), taking advantage of
  the return value to save some lines of code
- Modified callers to use the builders instead of directly
  calling the constructors

Change-Id: I713185d5ecbadbf51f87ef7f68fec41102106c78
diff --git a/cli/src/main/java/org/onosproject/cli/net/AddMultiPointToSinglePointIntentCommand.java b/cli/src/main/java/org/onosproject/cli/net/AddMultiPointToSinglePointIntentCommand.java
index abc0c4b..892f819 100644
--- a/cli/src/main/java/org/onosproject/cli/net/AddMultiPointToSinglePointIntentCommand.java
+++ b/cli/src/main/java/org/onosproject/cli/net/AddMultiPointToSinglePointIntentCommand.java
@@ -72,11 +72,16 @@
         TrafficTreatment treatment = buildTrafficTreatment();
         List<Constraint> constraints = buildConstraints();
 
-        Intent intent = new MultiPointToSinglePointIntent(appId(), key(),
-                                                          selector, treatment,
-                                                          ingressPoints, egress,
-                                                          constraints,
-                                                          priority());
+        Intent intent = MultiPointToSinglePointIntent.builder()
+                .appId(appId())
+                .key(key())
+                .selector(selector)
+                .treatment(treatment)
+                .ingressPoints(ingressPoints)
+                .egressPoint(egress)
+                .constraints(constraints)
+                .priority(priority())
+                .build();
         service.submit(intent);
         print("Multipoint to single point intent submitted:\n%s", intent.toString());
     }