* 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
