initial commit of new configuration access logic

1. Introduced new configuration manager class (singleton) based on apache commons composite configurations to load the config files during initialization
2. New configuration properties and their default values are maintained as enums.
3. qpid configuration classes were moved to "org.wso2.andes.configuration.qpid" from "org.wso2.andes.server.configuration"
4. MQTT configurations moved into andes config file
5. Added "commons-jxpath" since it is required by "commons-configuration" to handle xpath queries.
6. Added meaningful comments to describe properties and their usage.

Conflicts:
	modules/andes-core/broker/src/main/java/org/wso2/andes/kernel/AndesKernelBoot.java
	modules/andes-core/broker/src/main/java/org/wso2/andes/server/slot/SlotDeliveryWorkerManager.java
Change qpid config files namespace to "org.wso2.andes.configuration.qpid" instead of "org.wso2.andes.configuration.qpid.configuration"

Initialize AndesConfigurationManager at the QpidServiceComponent bundle activate event.

Log exception that occurs when retrieving configurations, even though the default value is applied.
Added missing license header
Merge pull request #170 from hastef88/configuration_revamp_m2

Configuration revamp m2