feat(HttpHeaders): Add constant for analytics header

Author: lpatino10

src/main/java/com/ibm/cloud/sdk/core/http/HttpHeaders.java

@@ -153,6 +153,9 @@ public interface HttpHeaders {
    */
   String WWW_AUTHENTICATE = "WWW-Authenticate";
 
+  /** Header containing analytics info. */
+  String X_IBMCLOUD_SDK_ANALYTICS = "X-IBMCloud-SDK-Analytics";
+
   /** The Authorization token header. */
   String X_WATSON_AUTHORIZATION_TOKEN = "X-Watson-Authorization-Token";