Setup PropertySource precedence for module props

- Allow PropertySources to have the following precedence when
  resolving the module properties

High 6 - CommandLine options ('moduleOptions' PropertySource)
     5 - System Properties ('systemProperties' PropertySource)
     4 - System Environment ('systemEnvironment' PropertySource)
     3 - ${xd.config.home}/modules/<moduleType>/<moduleName>.properties
         ('moduleConfigOptions' PropertySource)
         Note: this location is different from ${xd.home}/'modules'
     2 - ${xd.config.home}/config/<moduleName>.properties
         ('xdConfigOptions' PropertySource)
     1 - application.(yml/properties) fragment file:./ file:./config/ classpath:config/ & classpath:
     0 - application.(yml/properties)

- Fixed RabbitMQ source/sink
 - Removed propertysource placehoder configurer
 - Fixed 'virtualHost' property name
  - Updated the property to use 'vhost' as in RabbitSourceOptionMetaData