Configuration revamp - use of new AndesConfigurationManager for accessing properties.

Use new AndesConfigurationManager class to access andes-specific properties. 

Rename andes-config.xml to broker.xml and move qpid configurations to qpid-config.xml. 

move andes configurations to broker.xml and abstract qpid-virtualhosts.xml. 

Further Refactoring : 
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Please refer https://github.com/wso2-dev/carbon-business-messaging/pull/63 and https://github.com/wso2-dev/carbon-business-messaging/pull/65.
I don't think we need the toString here.