Prefix Variable Substitution

[VasuBalakrishnan]

Can we add variable substitution for prefixKey (very similar to NLog Layout Renderer)? This would be helpful if you're deploying services to multiple machines and would want to keep the config files same.

As an example:

<graphite xmlns="http://github.com/peschuster/Graphite/Configuration">
    <!--<graphite address="127.0.0.1" port="2003" transport="Tcp" />-->
    <statsd address="127.0.0.1" port="8125" prefixKey="${appsetting:env}.${machinename}.services" />
</graphite>