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/core/api/src/test/java/org/onosproject/net/intent/MultiPointToSinglePointIntentTest.java b/core/api/src/test/java/org/onosproject/net/intent/MultiPointToSinglePointIntentTest.java
index cab6a8d..2aac906 100644
--- a/core/api/src/test/java/org/onosproject/net/intent/MultiPointToSinglePointIntentTest.java
+++ b/core/api/src/test/java/org/onosproject/net/intent/MultiPointToSinglePointIntentTest.java
@@ -44,11 +44,23 @@
 
     @Override
     protected MultiPointToSinglePointIntent createOne() {
-        return new MultiPointToSinglePointIntent(APPID, MATCH, NOP, PS1, P2);
+        return MultiPointToSinglePointIntent.builder()
+                .appId(APPID)
+                .selector(MATCH)
+                .treatment(NOP)
+                .ingressPoints(PS1)
+                .egressPoint(P2)
+                .build();
     }
 
     @Override
     protected MultiPointToSinglePointIntent createAnother() {
-        return new MultiPointToSinglePointIntent(APPID, MATCH, NOP, PS2, P1);
+        return MultiPointToSinglePointIntent.builder()
+                .appId(APPID)
+                .selector(MATCH)
+                .treatment(NOP)
+                .ingressPoints(PS2)
+                .egressPoint(P1)
+                .build();
     }
 }