Refactor bucket delete and bucket policy (#5580)

This commit adds the bucket delete and bucket policy functionalities
to the browser.

Part of rewriting the browser code to follow best practices and
guidelines of React (issues #5409 and #5410)

The backend code has been modified by @krishnasrinivas to prevent
issue #4498 from occuring. The relevant changes have been made to the
code according to the latest commit and the unit tests in the backend.
This commit also addresses issue #5449.

browser/app/js/buckets/Bucket.js

@@ -16,6 +16,7 @@
 
 import React from "react"
 import classNames from "classnames"
+import BucketDropdown from "./BucketDropdown"
 
 export const Bucket = ({ bucket, isActive, selectBucket }) => {
   return (
@@ -36,6 +37,7 @@ export const Bucket = ({ bucket, isActive, selectBucket }) => {
       >
         {bucket}
       </a>
+      <BucketDropdown bucket={bucket}/>
     </li>
   )
 }