Android: preserve JSONException cause in setJSONValueForKey (#34)

The catch block had the original JSONException in hand but built the
CodePushUnknownException without it, discarding the cause and its
stack trace entirely. Pass it through so CodePushUtils.log(Throwable)
callers downstream actually see why the JSON write failed.

Author: ofalvai

android/app/src/main/java/com/microsoft/codepush/react/CodePushUtils.java

@@ -219,7 +219,7 @@ public static void setJSONValueForKey(JSONObject json, String key, Object value)
         try {
             json.put(key, value);
         } catch (JSONException e) {
-            throw new CodePushUnknownException("Unable to set value " + value + " for key " + key + " to JSONObject");
+            throw new CodePushUnknownException("Unable to set value " + value + " for key " + key + " to JSONObject", e);
         }
     }