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/BucketList.js

@@ -28,7 +28,7 @@ export class BucketList extends React.Component {
   componentWillMount() {
     const { fetchBuckets, setBucketList, selectBucket } = this.props
     if (web.LoggedIn()) {
-      fetchBuckets()
+      fetchBuckets("list")
     } else {
       const { bucket, prefix } = pathSlice(history.location.pathname)
       if (bucket) {
@@ -63,7 +63,7 @@ const mapStateToProps = state => {
 
 const mapDispatchToProps = dispatch => {
   return {
-    fetchBuckets: () => dispatch(actionsBuckets.fetchBuckets()),
+    fetchBuckets: action => dispatch(actionsBuckets.fetchBuckets(action)),
     setBucketList: buckets => dispatch(actionsBuckets.setList(buckets)),
     selectBucket: bucket => dispatch(actionsBuckets.selectBucket(bucket))
   }