[ONOS-3618] Implement REST API for Meter query, insert, delete

* Implement encode & decode method for MeterBandCodec & MeterCodec
* Implement MetersWebResource
* Add unit test for MeterBandCodec & MeterCodec
* Add unit test for MetersWebResource
* Add meter insertion json example
* Add Swagger doc

Change-Id: I07284c6678c08b3cb9e109e86ffb2cf28bf36447
diff --git a/core/api/src/main/java/org/onosproject/net/meter/DefaultBand.java b/core/api/src/main/java/org/onosproject/net/meter/DefaultBand.java
index 9bc9970..e46069b 100644
--- a/core/api/src/main/java/org/onosproject/net/meter/DefaultBand.java
+++ b/core/api/src/main/java/org/onosproject/net/meter/DefaultBand.java
@@ -45,12 +45,12 @@
     }
 
     @Override
-    public long burst() {
+    public Long burst() {
         return burstSize;
     }
 
     @Override
-    public short dropPrecedence() {
+    public Short dropPrecedence() {
         return prec;
     }