allow non-loggedin users to access public bucket (#5570)

* conditionally render main action buttons

- Make bucket action will be available only for loggedIn users
- File upload button will be avaialble for loggedIn users
  and non-loggedIn users if the prefix is writable

* select the bucket and prefix from the url

When the url contains bucket and prefix, it will be selected
by default instead of the first bucket from the list.

* show BucketSearch only for LoggedIn users

* allow non-LoggedIn users to access public bucket

* removed unused Router imports

* fix test case failures in BucketList.test.js

* remove dupicate minioBrowserPrefix from url

since history is already initialized with minioBrowserPrefix,
no need to use it in push or replace

* remove unused match from App component

* remove unused minioBrowserPrefix imports

browser/app/js/objects/reducer.js

@@ -32,6 +32,7 @@ export default (
     currentPrefix: "",
     marker: "",
     isTruncated: false,
+    prefixWritable: false,
     shareObject: {
       show: false,
       object: "",
@@ -78,6 +79,11 @@ export default (
         marker: "",
         isTruncated: false
       }
+    case actionsObjects.SET_PREFIX_WRITABLE:
+      return {
+        ...state,
+        prefixWritable: action.prefixWritable
+      }
     case actionsObjects.SET_SHARE_OBJECT:
       return {
         ...state,