Give ability to define constants that may be used throught the configuration

OpenSim/Region/Application/ConfigurationLoader.cs

@@ -213,6 +213,8 @@ namespace OpenSim
             // Make sure command line options take precedence
             m_config.Source.Merge(argvSource);
 
+            m_config.Source.ReplaceKeyValues();
+
             ReadConfigSettings();
 
             return m_config;

OpenSim/Server/Base/ServicesServerBase.cs

@@ -129,6 +129,8 @@ namespace OpenSim.Server.Base
             // Merge the configuration from the command line into the loaded file
             Config.Merge(argvConfig);
 
+            Config.ReplaceKeyValues();
+
             // Refresh the startupConfig post merge
             if (Config.Configs["Startup"] != null)
             {