Fix for MB-838 Unable to browse queues when user has a domain name

When the user name contains the domain name with the '/' character (eg: WSO2/admin),
queues can't be browsed from UI because the AMQP url generated for queue browsing
contains an invalid separator within the user name. Now this characters in
username field is escaped according to the URL standard using java.net.URLEncoder
Merge pull request #45 from Asitha/mb-838

Fix for MB-838 Unable to browse queues when user has a domain name